Again, someone has made the mistake of listening to the shop. Sales of Goods Act - your contract was with Comet, not Compaq, so any problems, etc are for Comet to resolve, up to six years after buying the goods from them.
I purchased a large LCD TV from Comet, which failed after three weeks and they tried to give me a run-around.
I finally spoke face-to-face with the manager and reminded them of the sale of goods act, and that I did have to give them the chance to resolve the issue, but at my convenience, not theirs.
They plugged it in immediately, saw it didn't work and gave me a replacement.
Their original answer was for me to wait in for an engineer to call and check the TV, give me a form and then return both to the store. Never again!