Internet Explorer Errors

I have been having trouble with internet explorer. I was on 5.0 and it lost it’s tool bar and would not browse to some pages. I finally got the toolbar back, but it still will go to some pages and say done, but there is no info on the page. I don’t even get the page not available message. I upgraded to ie 6.00 and I am still not able to view some pages. I also cannot right click or download files anymore since the upgrade (if I try to download, it opens up a browser screen with what looks like gibberish. I also cannot open add-remove programs to uninstall. I get an error message that says mshta.exe has generated and error and then closes. I am running windows 2k professional. Help!