Thank you for answering, although I live in Spain I am English and would prefer you write in my language please.
I do not know what an OS is and i work in windows XL
Are you still communicating with me???
Yes all four worked perfectly until recently, but one by one they have stopped working. the last one to stop working was 2 days ago.
I use the mouse, a printer and a web cam contstantly.
Yes I use Windows XP
I used the one remaining working port up until 2 days ago when it stopped working.
Yes I have done a system restore recently one week ago
I do not think the ports are loose because I get message saying "USB PORT NOT RECOGNISED. which I do not think I would get if they were loose.
I did as you explained, I uninstalled and reinstalled the USBs. A very interesting excerisise, but unfortunately it did not work. (very dissappointing). However, Here are the details of my computer:
It is a ADVENT 7105
It also has a label which says MOBILE AMD SEMPRON 3000+ if this information is of any use to you. Hope to hear from you soon.
Thank you very much for your invaluable help. I am so pleased to have my usb working again.