Holy SHIT.
Ok, 4 hours, 2 LiveCDs, several partition resizes, and a few reboots later, I finally got my computer working properly after resizing the Windows partition. Here's what happened: I deleted everything on the Ubuntu partition and redid the menu.lst in the grub folder, which worked out fine. However, there was no partitioner on the LiveCD I used. I had to burn another CD, this time remembering to put gparted in.
I booted up again, went into gparted, deleted the swap partition, and resized everything accordingly. But when I tried to reboot, I got grub error 22, which I'd earlier read meant that the partition wasn't found. I didn't realize why until I booted back up with a LiveCD: There are 2 hard drives in this computer. Recovery is hda1, main is hda2, I don't remember what was hda3, and hda4 was extended, which is made up of hda5 (swap) and hda6 (Ubuntu). When I deleted the swap partition, the Ubuntu (now just grub) partition was renamed to hda5. Grub didn't know this, it just assumed that I had gotten rid of an important part of it. So I rebooted, this time with the LiveCD that had gparted on it (I'd used the other one).
I tried simply renaming the partition, but that didn't seem to work. Eventually I resized the main partition (again), copied the grub partition (to hda6), formatted the first one (hda5) to swap, and shrunk everything down as small as possible to make room for the main partition. Now, although my computer boots properly, I have a useless 7MB swap partition.
Lesson learned: When installing anything for dual-boot on a computer that doesn't have a multi-OS bootloader, do the swap space last.