As mentioned in my Monday Morning Memo, I see a lot of folks who want to "Do It Yourself" when it comes to computer repair. Yes, with some of the proper tools, you can, but when it comes to many of the new viruses and malware out there, it's tough to do and do right.
Here are some tools to use for basic maintenance:
CCleaner -- Use the file cleaning part. (Download from FileHippo)
Defrag -- In many systems this is already preset for a certain time/day.
Error Checking or Check Disk -- Under tools in the hard drive area.
Updating your virus programs
Updating Flash, Java, Shockwave, Adobe Reader
Reformatting -- usually happens when you make the wrong choices on a DIY project.
However, much beyond that you are in a grey area that I don't even give advice to over the phone. You see, when I do, then I feel that I'm liable if you mess it up. Plus, doing a Google Search for some of this may lead you down the wrong path as well. Folks who run virus/spyware sites are usually pretty good at SEO and making their hacker sites bubble up to the top to make you think that you can trust them to remote in and fix the issue.
Usually, they just get your credit card info and they are gone.
I've used a famous quote a lot, and it fits here as well. "If you think hiring a professional is expensive, hire an amateur once!"
Again, give The Computer Guy a call if you have issues, I can get the problem solved the right way the first time.