When I get one of these calls, I tell them (truthfully) that I use Linux. They usually hang up before I can.

I moved to Linux when the problem the OP described became chronic. I had tried the various cleanup procedures described in the magazines - defrag the hard drive, clear out temp files, the recycle bin etc. etc. There reached a point where these seemed to have no effect so I downloaded Ubuntu and tried it and got my computer back again. At the time my hard drive was only about 60% full so I had enough space for a dual boot as there were some windows programs I wanted to hang on to.

So if you're prepared to spend time learning a different way of doing things installing Linux is another possibility. It certainly gave my computer a new lease of life and extended its life by about 2 years. Now I wouldn't go back to Windows even though I gather that windows is much improved since Win7.