So I wasn't really thinking clearly, and deleted my XP partition, rendering me unable to boot at all. I get the NTLDR missing error, and I've tried repairing with my W7 disc. The start-up reparation tool tells me (I'm running a swedish version, so this might not be the exact wording) that there is no valid system partition in the partition table, and that it's going to repair it. Running it several times produces the same result, and does nothing to help me. I have also tried running bootrec.exe, which identifies my W7 installation, but when running rebuildbcd, trying to add the installation to the start-up list, or running fixboot, it will say that the element cannot be found.
I reinstalled XP on its old partition, which resulted in my Win 7 install disc finally realizing that there was a Win 7 installation on my hdd. After that, it managed to fix itself with the start-up repair tool, and now I'm running only Win 7 successfully.