Found an old Radeon X1300/1550

[Adiamante]

Is it even usable for pool mining? This thing is a little dusty 

[SgtSpike]

No.  Only 3xxx series and above ATI cards can utilize OpenCL.

[Adiamante]

4200 can't either. Might just but some BTCs if it price stays stable instead of buying a new card.

[BinaryMage]

4200 can't either. Might just but some BTCs if it price stays stable instead of buying a new card.

I'm assuming you mean buy. The future of mining is a little uncertain at the moment, what with the rapid difficulty increases and all. If I were you, I'd sell both those cards on Ebay and use the proceeds plus some extra cash to buy a cheap mining card, like a 5770 or 5830 if you can find one.