Not familiar with your specific problem, but here's a step-by-step on how to restore a wallet backup after reinstalling:
1. Install the client again (you've already done this)
2. Start it by running "bitcoin.exe"
3. Wait for the entire blockchain to download (you need this many blocks:
http://blockexplorer.com/q/getblockcount).
You need at least one "connection" to start downloading the blockchain. The number of connections is visible at the bottom right of the original/standard/"official" client (which you seem to be using).
4. Once you have downloaded all the blocks (152893 at the time I wrote this), exit the client, wait until it has shut down and paste your backup copy of the wallet.dat into AppData\Roaming\Bitcoin.
5. Start the client again (bitcoin.exe) and wait a short while to see if your coins "reappear"
Actually, Therelith, it's better to restore your wallet backup
before downloading blocks - the wallet balance is updated while the client is scanning the blocks as they come in; if you have downloaded the entire blockchain and then replace the wallet, it likely won't show a proper balance, and you will have to launch bitcoin.exe -rescan to have it find the missing payments.
It sounds like Dashwood is clicking on the installer over and over again, instead of launching the installed client.
bitcoin-0.4.0-win32-setup.exe is not Bitcoin and is not your wallet! It is the installer you downloaded, you run it only once to install Bitcoin on your computer, and then you should not run it again. Launch Bitcoin using the Start Menu -> All Programs -> Bitcoin -> Bitcoin.
The first thing to understand is that uninstalling and reinstalling Bitcoin doesn't erase your wallet.dat file (the file with a record of all your addresses and private sending keys). Bitcoin knows how important this file is, and will leave it on your computer even after uninstalling and reinstallation; you'd have to manually find and delete it. If you launch Bitcoin, and your old address is still the address shown at top or is in the address book (in the receiving tab), then you don't need to worry about restoring anything, you are still using your original wallet.
The full location of the Bitcoin user data directory on Windows 7 is C:\Users\{username}\AppData\Roaming\Bitcoin, where {username} is your windows logon name. Windows has a shortcut to get there: click on the start menu button, and in the search box, type
%APPDATA%\Bitcoin. Press Enter, and it will launch Windows Explorer and show you the contents of the correct directory.
Secondly, Windows 7 comes in a "dummy mode" that hides the full filename from you, which can cause big problems. To disable this, in the Windows Explorer you just launched, click "Tools" in the menu, and choose "Folder Options". Go to the "View" tab, and in Advanced settings, uncheck the box for "Hide extension for known file types" and press OK. This will prevent you from making mistakes.
If you didn't previously know this information about locating your wallet, or didn't verify that Bitcoin was completely terminated, it is likely that any "wallet backup" you made isn't actually a good backup. In the data directory, the wallet.dat file is your wallet file. This is the file that you should copy to a USB stick and put away, but only copy it
after verifying Bitcoin is not running at all (not even in the tray by the clock) - if you don't completely close Bitcoin, the backup copy of wallet.dat file will likely be bad. Close Bitcoin now, verify it is closed and close it's icon in the system tray if it remains.
If the central problem is that you started getting database errors like you describe above, then there are several particular files in your Bitcoin user directory that you should delete (or simply rename) to erase the corrupted transaction blockchain and force it to re-download:
1: blk0001.dat
2: blkindex.dat
3: any log files in the "database" directory (inside your Bitcoin data directory.)
After you launch Bitcoin, then it should get up to eight connections to other clients (or more if you have properly forwarded port 8333 in your router to your computer). It will take several hours to get all the transaction blocks; after a minute or two of making connections, you should see the block count on the bottom of the client start increasing from 0 blocks. You will only see Bitcoins that have been sent to you after Bitcoin has downloaded all the transaction blocks.
If you are getting 0 connections or block downloads don't start, first uninstall "Microsoft Security Essentials" from you computer if you have it, it is known to mess with Bitcoin. Other antivirus programs like Norton or McAfee that have firewall "features" can also mess with these connections. Finally, make sure you did correct port forwarding to your computer on port 8333, misconfiguring it can be worse than not messing with port forwarding at all.
