Sounds like a re-install would do you some good, but probably worth setting 100gb of that for an XP install, where you can have DBPro and modelling packages etc.
No matter how good your virus software is, a virus will often leave poop behind, in your registry for example, or even just as a file. But the main thing is to start out neat, and try and keep it neat - that way it's easier to avoid getting swamped and saves time in the end. For instance, deciding where to put the projects folder. You could put it in beside C:\Program Files\thegamecreators\darkbasic pro\projects - or - c:\Projects. I have to find my current project in it's folder all the time, in explorer, when saving files etc; shaving a few seconds off that shaves about 80% off the annoyance factor.