I am currently experiencing multiple problems with my computer and was sent here to look for help. Problems include severe slowdown on a relatively new machine, only one out of 4 accounts will connect to the internet, wont allow installation of programs such as McAfree privacy software. These are my main concerns, although there are a few other problems. Any help you can provide would be greatly appreciated.

Doc

I suggest posting a HighjackThis log in the Spyware Section (not here).

please follow owen's Instructions and then post your log in the Spyware, Adware, Viruses and HijackThis Logs section.

If after following owen's instructions your problems persist reply to this thread with more details such as exact error messages.

What, if anything, is different in the one account that will go online?
Is it the Admin account? Are the others Limited?

Did this machine work ok before? Did this just start happening? etc.

Also: look in your event viewer: rt. click My Computer then click Manage then Event Viewer.
Open the system as well as the application tabs & look for X errors. Click error line for details. Post back the source & event id of recent errors.