"OS X can not be installed on this computer"

[BeachChair]

I'm trying to fix restore my girlfriends (early 09) Macbook from a backup.
Its install discs are missing so I'm using the install disc from a (late 08) Unibody.
When I boot to the install disc I get the message "OS X can not be installed on this computer" and get the options "OK" and "Restart". Bewildered, I click OK and go into utilities and pick "Restore from backup", but nothing happens.

I'm not sure where to go from here, is it refusing to install AND restore from backup because the DVDs belong to another computer?
Or is something entirely different wrong.

 

[Hellhammer]

You can't use your Mac's restore disks as they are system specific. Grab a Snow Leopard for 29$ and install that

 

[hamlinspahn]

OS X disk

OS X recovery disk are hardware specific. If it didn't come with it or one exactly like it it won't work and an 09 MB to 08 MB are likely not to be the same they could be though. But the year isn't as important as model number.
Full OS X disk do a hardware check also so one that is older than the MB would not work either as the newer MB would not be a recognized model.