Thanks OneWorld22 and Wedge - but I don't think Sasser is the culprit in this case - I ran the latest version of Stinger which looks for two variants of Sasser - and the symptoms are different but there as similar lofty50's problem. This is taking off a tangent somewhat.
I just completed another full scan with the disk as secondary in my own PC - it came clean so I'm left with a reformat. However I will try hijack this and let you know what's up E-Liam - thanks for the suggestion.
Cheers
Charles