Yeah, I remember being afraid of breaking computer parts putting them together or taking them apart. Then, after I accidentally dropped the screwdriver, pointy end down, on a few important looking circuits on the motherboard and it kept working, I realized that things weren't that fragile.
I'm often a bit afraid of running some games for a long time when I hear the video card fan going ten-to-the-dozen and feel the computer case warming up. I'm frightened some part I can't afford to replace, like the graphics card, might wear out and overheat. It's not particularly rational, I suppose...
You can install software to check on the temperature of your CPU and video card to ease your paranoia :) Most of these programs can even start beeping loudly if you are getting close to overheating the hardware.
That said, high-power modern video cards work at ridiculous temperatures, around 95C. That's almost enough to boil water, and yet is considered acceptable. Any modern CPU will shut off if overheated.
Anyway, you will probably have to replace your video card due to obsolescence rather than thermal damage.
