In my Microsoft PC days I would take it to be commercially repaired.
Got my first pc in early '02 which got ruined by a 'Windows Update, replaced that one in '06 and had it 'repaired' twice and I found the second repair unsatisfactory. 3 weeks after the second repair really strange things were happening. My Norton was due to be renewed and instead I downloaded Microsoft Security Essentials; very satisfied, it found a lot of stuff, but I had to manually download and install the updates.
So I started reading pc forums and such... and ran across "CCleaner.com" one evening. Installed (free/no $$) and ran that and WOW, the garbage it found and eliminated. Shut down 'puter' and went to bed. The next morning at start up in comes a windows update.... says it would take over an hour....so I sat and watched...low and behold it is doing 'service pack 3' which was supposed to be on the reinstall from the pro that last time I had it in to be fixed.
After that and regular maintenance using CCleaner it ran like a 'charm', absolutely no problems....until the hard drive finally died...dead...
So I bit the bullet and this past Dec. bought a MacBook (white).
Love my MacBook and have no idea when it will need 'servicing' but also bought the three yr. service plan, as I am such a dufus when it comes to computers and such.