Hey Caz08,
It's a shame to hear this
In this case you'll need to either contact Dell to get this sent back for repair, or you'll need to re-install Windows via network install. This latter option can be somewhat... tricky... um... so not something we could really advise on. If you've never done this, I would recommend against.
Unless you can find someone to help or do a network install for you, your easiest route will be to contact Dell and arrange a repair. You can contact them on 0844 3381000.
Let us know if we can help further!
Daz
eForum Team