I spent £70 buying Microsoft Office 2007 the other year, and have installed it numerous times on my own laptop (each time I reset it back to factory settings each month to keep using other trial software). I also installed it on my brother's laptop, and my dad's PC downstairs. Went to install it on my girlfriend's PC, and when you have to activate it over the internet, it said the product key had been used too many times. The liscensing agreement says I can install it once on three devices. Now I'm annoyed that should I ever need to reset my laptop back to factory settings, I won't be able to install it again,

Is there any way to bypass this? Like moving the liscence from my dad's PC to my girlfriend's laptop?

You can uninstall it on one system and reinstall it on another. You need to contact MS for the operation. But if you just reinstall it on the same system because you had to reinstall Vista, there should be no problem. The EULA says 3 PCs maximum - but reinstalling it on the same PC several times is still 1 PC.