H/W Diagnostics:
Please start by running these
bootable hardware diagnostics:
Memory Diagnostics (read the details at the link)
HD Diagnostic (read the details at the link) - Test
ALL of the hard drives.
Also, please run one of these free, independent online malware scans to ensure that your current protection hasn't been compromised:
Free Online AntiMalware Resources (read the details at the link)
There are also free, bootable antivirus disks at this link:
Free Online AntiMalware Resources - Bootable Disks