Problem with user settings/old apps trying to install themselves

[zx2012]

We're using Windows Server 2003 R2 and Windows XP SP3.

 

All of a sudden since half term(from the start of last week) All the teachers have lost their user settings*. ActivPrimary 3 keeps trying to install itself too. We've been using ActivInspire since July.

 

Icons on desktop not quite right.

 

Also there is one PC that tried to install some software we havn't used for year everytime someone logs on.

 

I wasn't in at all last week so I no that I have changed nothing. It's very hard where to start looking? Any ideas?