It depends on lot's o' stuff dude. A whole lot of stuff.

I'd be suspicious of a few of those ports, search this site and google for adware or trojan removal tools, or something similar. Scan with an updated antivirus. Unless of course you know why you have 5000 and the other odd ones open.

To close them easily and simply, get a firewall. Search google for windows firewalls. There are MANY threads on this site about recommended firewalls, use the search thing at the top right of the front page.

If that's Windows XP your running, learn how to use the built in Internet Connection Firewall (ICF) This should suit you just great. It's nice and simple to use.

If you still don't find enough answers from google to satisfy you, let us know. But alot of this stuff has either already been asked on this site, or has been covered extensively elsewhere on the internet.

- Good Day.

Jon.