System Corruption

Have had to reinstall ME on this computer 3 times in the last month. It's a Presario running ME. After a week or two I get the Windows New Hardware found wizard on boot up. But where the new hardware should be it's blank. Can't get beyond it even in Safe Mode. Just goes to a GSOD (Grey Screen of Death).
After reinstalling ME and fiddling with some other stuff (eSafe antivirus was corrupted and had to be reinstalled) it 's back to normal for now. Have run AdAware, SpyBot, etc, which found minimal infection. HJT log is clean.
Any ideas?
Hardware problem?

Order of suspicion: Memory, HDD, mobo...