i heard that if i make a limited user account only that account will get contaminated if sumthing happens to it. Is this true?
You can gain some security by using a limited account, but many of the nasites on the web get around permissions by sneaky ways. If you are running Vista 32 bit a better solution for safe surfing may be to try Sandboxie. The free version actually does what you need. The paid version has a few more features that make it easier to use(esp. with downloading files.)
Basically Sandboxie keeps the program that is running sandboxed from directly accessing the hard drive. When it thinks it's writing to your registry it's really writing to a reg settings file inside the sandbox folder.