Which ones? There should be HJT, MBAM and SAS. You can uninstall HJT but keep MBAM and SAS and run scans with them occasionally. here is a list, Software inspecter, Malware bytes, Moa2008use.exe, Superantispyware, Windowsxp-kb884020-x86-enu.exe, software inspector, Tinsetup, CCleaner, Noscript.
ANOTHER strange thing is happening. When I GO to "MEDIA CENTRE" and then close it I end up with a MSN MESSENGER icon on the bottom right which says not signed in when I put the cursor on it. If I log off and back on it is gone. I was having trouble with email but now is OK. I am prevented from using youtubr and similar sites
You can use the online Software inspecter so you don't need to have it installed.

Malware bytes & Superantispyware - Keep and run a scan occasionally, every two weeks or more if you think you need to. Remember to update before scanning.

That is an installer for something, but not anything I had you use I don't think. Delete it.

Windowsxp-kb884020-x86-enu.exe - Is an update for Windows XP Service PACK 2 (KB884020) - Did you already install it?

Tinsetup - I don't have a clue what this is. Nothing we use here.

Noscript - That is a Firefox add-on. Where do you see it at?

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Run this Disable/Remove Windows Messenger to the Desktop to remove Windows Messenger.

Do not confuse Windows Messenger with MSN Messenger because they are not the same. Windows Messenger is a frequent cause of popups.

Unzip the file on the Desktop. Open the MessengerDisable.exe and choose the bottom box - Uninstall Windows Messenger and click Apply.

Exit out of MessengerDisable then delete the two files that were put on the Desktop.

See if that takes care of the Messenger pop-up in Media Center.

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I am prevented from using youtubr and similar sites

the tinsetup ia winpatrol.
I have avast antivirus will any of these other programs malwarebytes or superantispyware conflict.