I have a dell xps m1210 laptop with windows vista home basic and i want to backup my hard drive with an external hard drive. I have seagate 500gb. Whenever I try to back it up it would say that "Disc C has errors. You must check the disk for errors before it can be restored" So i click Check the disk for errors, but when I click it it says "Windows can't check the disk while its in use". So how do I go about this?