Re: Major problem
Try booting it with a Win98 startup disk and do a "FDISK /MBR". This fixes the master boot record and leaves your data in tact. (Some boot managers use MBR though - they will get wiped out. If that happens use Disk Director or FDISK to set the partion you wish to boot from active).
*Fact: Microsoft Window's Blue Screen of Death vs Computerforums.org's White Screen of Death. Which is worse?