Just to say that I bit the bullet today and followed the advice proffered on this great forum and, fingers crossed, I succeeded in getting rid of the System Check virus. Even more pleased that the procedure only needed to be done once for my dual boot configuration which incidentally will now be quickly switched over to a cradle system so I hopefully won't infect both at the same time!
Now for one more question.....is it possible that my laptop (used wirelessly and fairly infrequently) is now carrying the same System Check virus?
Thanks for the help so far which is greatly appreciated.