Hard drive on the fritz

Problems with my PC, yet again, seems like any time I want to do anything productive, I have to rebuild my computer first... This time it's either the SATA 120GB Western Digital hard-drive or the Promise SATA 150TX2Plus Serial ATA Controller card. I've had them for about 4 months, and haven't suspected anything wrong... Clearly, I have problems with the HD: files appear to be corrupted, and about every other boot XP decides to scan the disk and correct problems with invalid entries in indexes, corrupted attributes, orphaned files. Each time it tries to resolve problems, more files appear to become corrupted. My data drive and OS are installed on the same physical drive, but on different partitions. The problem is spanned across both partitions. Last night, the system became completely unbootable. In Safe Mode, CHKSDK produced the "This volume has one or more unrecoverable problems" error. I reinstalled the OS on the same partition without formatting (I needed some data off that drive) I'll try to back up my data drive, purging old data as I go and then do a full format of the drive. I've also noticed that newer drivers are available for the SATA Controller card, which are digitally signed: the version I'm currently using is not. I left the house this morning with a disk diagnostic running -- it should be done by the time I get home. If the drive checks out fine, then I'm going to blame the SATA controller. The irony of this is -- about two months ago, I gave my mother my perfectly good 40Gb Western Digital DMA/133 drive. Hopefully I can get things back up and running without having to buy an external drive or something.