There are dozens of reasons for causing these symptoms.  It could be a bad hard drive, viruses, spyware, a bad motherboard, bad memory chips, too many startup items or corrupted windows.  Most likely, it is a combination of more than one of these.

We will check your desktop PC for blown capacitors, for free, while you wait.  This only takes about 2 minutes.  If we find this problem, then you are most likely going to need a new computer, rather than the current one fixed.

Then, we run a full hardware diagnostic which tests your motherboard, memory, video card, power supply and hard drive.  This takes about 2 hours.

If all those pass, then we test to see if it is a virus, or spyware, which is causing these issues.  This takes about 4 hours.
So, the diagnostic is only $40 —  Payable AFTER the service is done.