Hard drive controller crashing my drives?

Hi there,
I have an older desktop PC that I’m trying to revive so my kids can use it.

Twice now I’ve formatted a hard drive, installed the O/S (WinXP), and installed all the software. After a few days, the disk no longer books, with the BIOS complaining there is no boot sector.

I used a different hard drives in each of my tests, and afterward I tested each in an external enclosure, and verified that they were working fine.

I find it extremely unlikely that both drives had random errors precisely in the boot sector. Therefore, I suspect something else is corrupting the boot sector. The hard drive controller?! What else?!

Any thoughts on how to diagnose the problem, or what I can do, would be appreciated.

Thanks.