Okay, first of all, you shouldn't put that many sites on your computer. If your computer crashes, its going to take a long time to get back all of those websites. Since youre running that kind of computer, its going to be a risk of having that many sites, unless you upgrade it. You can also get a hardrive storage chip so you can store your sites, as backups(in case your hardrive crashes) and to mabye free up some memory. My best guess, a regular site usually takes up about 10-150mb of hardrive space, which means that you need to watch out if you don't want to lose a ton of websites.
Best Of Luck!