|Sometimes you'll have an option on the posting screen to choose the boot partition.|
I had a similar problem with a Dell not long ago and used a dos program called PTEDIT to change the boot partition. There's some info here:
Boot to dos, run PTEDIT and change the recovery partition's boot indicator to '80' and the other partitions to '00'. Then reboot from the hard drive. (The instructions on the site above say you need to boot from a win98 bootdisk after changing the boot partition but since the recovery partition is bootable you don't need to do that.)
After running the recovery you probably won't need to run PTEDIT again as the recovery process should reset the boot partition info.
If your windows is currently working you may be able to download PTEDIT32 and run it from a command prompt.