What is the make and model of the computer and what edition of Windows are you running?
If the old product key is for preinstalled Windows (and I assume it is) it will not work. For the old key to work again you need to restore your laptop to factory condition and just get rid of the non genuine Windows. The only other alternative
is to buy a new copy of Windows, which you don't want to do.
If the recovery partition is still intact just try whatever F-key combination is needed as the computer starts. However, your friend's software may have overwritten the key codes stored at the factory. If so you need to order recovery disks
from the manufacturer or from a third party. Find third parties by googling on "recovery disks". Several companies will sell you a set.
Colin Barnhorst Windows 7 Ultimate x64 on DIY with 6GB ram.
