Since the 8th didn't activate, that means it IS a power issue.

Remember that USB hubs after the 4th port tend to just add another "hub" to the 4th port to give you another three.  Since the computer is so old I suspect that the USB ports don't give enough power (despite the power block) to power the ASICS.  Not to mention that you should be able to only run 8 on this rig (anyways) since there isn't enough current to power all 10.  Each ASIC requires .5 A and 5V for a total of 2.5W.  The hub's power supply can give (at max) 4A.  This doesn't account for additional current draw from the USB port.  Basically to get a ten port HUB you have to use three hubs. 

PC USB -> Hub 1 (3 ports available)
Hub 1 port #4 -> Hub 2 (3 ports available)
Hub 2 port #4 -> Hub 3 (4 ports available)

3 + 3 + 4 = 10 ()

Now for a little on the HUB.  Remember that when using a HUB the USB ports of the HUB (without power supply) must share the .5A/.9A/1.5 A (in order USB 2.0/3.0/Dedicated charge) across all of the ports.  However when you throw a power supply into the mix the amount of available power per port drastically increases.  Older motherboards may only give .5A (USB 2.0) which would at best allow you to add in one more device but this is also used to power the additional "hubs" to get more ports.

What confirms this is a power issue IS that it works on a newer rig.  Many new motherboards and systems have what's called "dedicated charge" ports along with USB 3.0.  With the move to USB 3.0 the total current draw was increased to 900mA and dedicated charge ports are rated up to 1500mA.  However, on an XP machine I doubt that you have USB 3.0, most likely (99.99% chance here it's) USB 2.0.  USB 2.0 is rated at 500mA maximum, not counting dedicated charge ports which on an XP era machine were RARE (usually a different colored port to check-> yellow/blue as red indicated eSATA/USB combo).  With the additional .5A you *could* run 9 ASICs but that's NOT taking into account the power that the hubs require, which is probably around .5A since you can't use more than 7 ASICs on the XP machine.

On the newer rigs USB 3.0 ports tend to put out around .9-1.5A (if dedicated charge) so people can charge tables and such without having to use a wall outlet.  So if we add 1.5 A (i3) + 4 A(hub) = 5.5A/.5A (per device) = 11 devices on a dedicated charge port.  However, even if we use the .9A that's 4.9A which gives you ~9.8 ASICs powered.  Since we know that the hub uses ~.5A you still have enough room to power the 9th device (with some wiggle) on a .9A port and 10 on the 1.5A but NOT enough to power a 10th/11th accordingly (I know the hub is 10 it's just a part of the explanation).  Normally I'd say use one less than the max possible (available Amps / .5A) but since you have to subtract 1 device (or .5A) to account for the HUB this is taken care of for you since in most configurations you'll have MORE than the needed power for MAX-1 ASICs but not enough to fully power the last (-1) ASIC.

So, this can't be a driver issue or Hub issue since 7 of the ASICs work and this shows that Windows XP is detecting the devices since if it was a driver issue NONE of them would work.  Because the 8th just doesn't do anything, it tells me that the older USB port just can't provide enough power to run the additional device.

As for your question about testing, unfortunately manufacturers are greedy and like to cut corners.  If they reduce the power to a USB port (or use the absolute minimum) they can reduce some heat that goes through the system (along with wasted power).  They also like to include power supplies that *just* barely have enough power to power the system under load (sometimes not even that).  So it's going to be hit or miss on this. 

I'd recommend trying to find a mid-2011 mac mini (obviously used) since in 2011 Apple implemented 1.5A per port so you could charge your i-devices without issue.  Currently I am running 36 ASICs off of two ports, daisy chaining the hubs a bit (7 port hubs) to give me enough connections and it's been running smoothly (with no hiccups) for about a month now.  However, I do have enough USB ports to add in 10 more ASICs but since the power supply is only 3A I can run at max 6 (but the 6th doesn't have enough power since I have to daisy chain to power so many on this rig) so I'm only able to run 5 per HUB.

So while I'd love to tell you that this is a driver issue and windows XP is just not doing it right, this really is a power issue.  Go buy another USB hub and save yourself the headache.

Ok, so there's actually a few things.

1.) This should be fine for what your doing.
2.) Ok, you can most likely put 3 ASICS on the back of your PC but I wouldn't recommend doing that, good way to fry a motherboard should the current be more than what it can handle.
3.) The two ports can host ONE miner.  That is all.

4,5,6)  This hub isn't going to be powerful enough to run all of these.  At most you could put 7.  Yes, the math (2.5W = 5V * .5 A) means that you *could* put 8 ASICS in this one hub (4000ma = 4A/.5A = 8 ASICS possible) but really you can't.  The ASICS user power to both mine AND send/receive data.  The draw will be too high and the hub might not be able to compensate even if it pulls more from the computer.

7.) it's an older model which confirms that the USB ports might not be up to snuff.  Manufacturers like to cut corners with power and the best place (was) to under power the USB ports.  Though they can run USB 2.0 devices most devices require less than the maximum power to run.

As a test, try plugging in 7 devices into the hub, then get mining running.  Once it's stabilized (wait like 5 minutes) try to add one more ASIC and WAIT until the light stops flashing on it and turns a solid green.  If your mining software detects it and starts work, great try adding one more until it stops working.  If it stays green see below:

If your using bfgminer you must get the com port that the new device is running on (open device manager while adding it) and press M then + (manage devices, add new device) then type in the corresponding COM port (e.g. //com8).  If it says No New Device (or no device found) then the device can't initialize and however many you've added to the HUB is the max that HUB can support.

If your using CGminer (with ASIC support) it should automatically detect the new device and just start working.  Keep trying to add (once the 7 are stable) until NO additional devices are recognized.  This is the max that the HUB can support.

BTW.  For all of you who say it's a driver problem your wrong.  His computer "sees" 7 of them, which means the drivers are working correctly.  3 (assuming OP bought 10 for a 10 port hub) don't have enough power to run.  He needs to either get another HUB and run 7 in each OR try using the ports directly on his motherboard (not recommended).  It isn't a driver issue here it's simply that the ASICS aren't getting enough power to run.

On a side note, try stopping the mining software and plugging them all in, they should all light up (solid green) because with NO work they only require a very small amount of power.

Also as otsaku said, try plugging each device in (alone) to the hub and see if it can start mining if it doesn't it might be bad (DOA).

Please let me know if this helps you.

Try bfg miner, i use under win8 and is super, he recognize difrent hardware automaticly.

Ps. Renember about drivers

Hey, could you please detail your rig?

Please give us the following so I can help you better.

1: Operating System
2: Onboard USB Ports
3: Front Panel USB Ports*
4: Ports on Hub
5: Hub Power Supply Details (typically on the power brick's sticker)
     -Input Voltage
     -Input Amps
     -Output Voltage
     -Output Amperage
6:  Where you are plugging these miners into (which ports on the HUB and the computer itself)
7:  If applicable: Computer Brand and Model Number

*3, front panel ports are usually connected via a cable to the motherboard and the available power is typically less then that from a USB port on the motherboard.  On my system I have two sets of Front end ports, 1 set of USB 3.0 and 1 set of USB 2.0.  Since they both require separate headers I can plug one USB miner into them no probrm (giving me the ability to use 2 miners on the front ports of the system).  I cannot test more because of the placement of the ports (their horizontal not vertical (grumble grumble)).

You have stated that your system is Windows XP so the motherboard *may* not be up to the task of supplying the proper power to the devices.  If the HUB isn't powered then your probably never going to get them working.  Please get me (at least some) of this information so I can help you more.