Question Author
Thanks to you all for being so helpful.
Methyl, I removed some 'unwanted' files/programmes from my XP desktop before attempting to set up my new Windows 7 desktop and tranfer data from old to new, but must have inadvertently removed an essential driver because I then lost my local (Virgin Media Cable) connection to the internet.
After spending 3 hours talking to their help-line techies in India, who took me through the checks you suggested,the problem remained and it was decided it was a lan card/driver issue.
I've now taken the faulty pc to my very good local repairer who has quoted a basic £25 fee. Although I can follow a set of instructions I am not a skilled IT person, so thanks once more.
D
PS I am using my temperamental laptop at present.