After buying a 2nd hand virus c desktop I had problems with it dropping out, audio stuttering, shrieking etc and went through these steps to attempt a fix: system reset, change cr 2032 battery, change power pack, upload new os.
The os update was such a pain in the #$@# that I made a very amateur vid of how to do it:
Also I uploaded a pdf here with detailed instructions.
I reinstalled the os a couple of times as I was still having dropouts and crashes requiring a restart. Fingers crossed it worked this time.