When you still have a guarantee and customer service cannot help you so you have to leave your PC at a depot so they can fix it you are given a specific number (not an actual tag usually) and this number is your work order- withiut a number they will not fix it. This is how it worked for me last year with my PC. Note that they give you online service first, noone comes to your house for the normal kind of guarantee - you must have an extended guaranteee for that kind of service.