Thanks for your reply .... it was reassuring, but when I run superantispyware I still get the Trojan detected.
I updated Java (to JRE 6 update 6) then ran Superantispyware.
It detected Adware Tracking Cookie in Docs & settings \ myname \ cookies, which isn't really a problem as they are easily removed (but puzzling since most cookies go into temporary internet files).
It also reported Trojan Vundo-Variant / Small located in c:\winnt\system32\prsaxara.dll
Again it was easy to remove but why does it keep coming back? The computer is running ok ... does it really matter (I probably wouldn't even know about it if I hadn't started using Superantispyware ... Spybot doesn't detect it!)
Thanks
Paul