If your laptop came without a physical Windows installation disk, then it should have had some information on how to do a factory restore in the event of a corrupted OS.
Some manufacturers allow you to burn a recovery disk/disks when you first boot the machine which you can then use to "recover" your system. Other manufacturers use a partition on the hard drive to store the recovery files and yet others use a combination of both.
I would try contacting either PC World or the manufacturer of your laptop and explain what happened and how to go about doing a factory restore, they would be able to give you the best advice on what to do. As the original hard drive is dead the recovery partition option, if one was used, is also gone but you might be able to buy DVD disks from the manufacturer to restore rather than pay for a new Vista OS.
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