Hi
Well, first of all you need to make sure that Internet Explorer (I.E.) is properly installed and working. Open Control Panel, open Add/Remove Programs and scroll down to Internet Explorer. Double click it and you should see an option to repair it. Try to repair it.
Next, connect to Windows Update (if you can) and scan for updates. You should download all available critical updates if you have not done so already. Included in these updates are service packs and updates for I.E.
Next, run several spyware/adware checkers - Microsoft AntiSPyware, AdAware, SpywareBlaster (assuming you can download these of course).
Finally, check for viruses on your machine.
If you still have problems after trying these tips, reject this answer and describe any errors you get or other strange behaviour.
Good luck