xp not operating, Linux working

I have posted this to the virus removal thread but not sure if it is an XP specific problem so here it is:

I seem to have a virus attack on my PC running XP with SP2, neither Spybot or AVG seem to touch it. The symptoms are as follows:-
1) I can't access the web because a message says that my browser is already running but it does not appear in Task Manager

2) When I try to open a folder to access programme files in explorer or My Computer the dialog box for "OPEN WITH" comes up instead of the usual list of files.

There are other less specific symptoms such as my desktop colour has reverted to the default setting, the programmes I can run are very slow and there seems to be a lot of HD activity.

AVG suggested a "Mediapipe" infection but running a SmitFraud removal tool in Safe Mode has done no good.
Fortunately I have Ubuntu Linux co-loaded on my PC which enables me to contact you. (Last time I use peer to peer!).