Thankyou for the help everybody, it is very much appreciated.
I haven't had a chance to go to my mum's to try anything yet, but I did find out from her that when she starts up the computer, the very first thing to load up is a text file titled " Larissa you muppet ".
I searched for the above in Google and found out that the Virus is called W32/Sumom-C.
Should hopefully be able to get rid of this thing pretty soon. (Y)
Thanks again.