|Crashes can be from a number of reasons. Since you stated you had virus issues then there could be all sorts of other file issues. The only way to prove it is to do a complete reload from known good media. Follow that by using best practices to avoid this in the future.|
Second is hardware. This could be all sorts of issues to failing parts and temperatures.
Places to start. See event logs for clues. See if any dump files exist.
See bios for any temp settings.
Might be a board flex.
Re-seat all removable components. Be sure to follow esd and discharge PSU before you remove any components.
It should go without saying but remove and tag out the AC power plug.
Use a diag tool like ultimate boot cd and start with memtest.
Use live cd's to see if system is stable. Make a barts pe cd.
Basically one question of course would be did it ever work well? If so you may be able to get it back.
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