Since XP knows nothing about SATA that BIOS flash could have reset the BIOS defaults to "native SATA" instead of "emulate IDE".
I see no link to your motherboard's documentation but given the story, that's my bet.
Me and my boyfriend currently have two custom made computers, both with WINXP (ones an aspire and one alienware, not sure of the exact details.) anyways, the aspire has a KN1 SLI lite 1.0A motherboard and a new 500gb harddrive (seagate). We just got them back from the computer place and they told us the only thing wrong with the aspire was the HDD, buying the new one didnt resolve our problem though? It will now turn on without going to the BSOF , but still will not download games off of CDs or the web (steam, ect.). We got them fixed to be able to play GW2 and thats exactlyu what we CANT do . Ive been searching problems on the internet and havent found anyone with the exact same problem unfortunately. We recently tried flashing the BIOS though and something went wrong I think, we backed up the bios before. Now when we turn it on though it gets stuck at the windows loading screen. HELP ?