Help! Windows 2K installation

I have a four-year-old Sony Vaio Desktop. It came with Windows 98. One year ago, I partitioned the hard drive and installed both windows 98 and Linux. Since Linux constantly crashes, I reformatted the hard drive and tried to insall Windows 98 using the origianl installation CD. The insallation process failed. Then I tried to install Windows 2000. It succeded with some warnings. After using Windows 2000 for a while, it started to crash constantly. I tried to format hard drive and install Windows 2000 once more but every time it failed.

Can anybody tell me if it's hard drive failure? When I formatted the hard drive, there is no warning or any sign though.

Thanks in advance!