Windows 7 Killed Vista

I installed Win7 RC 7100 on my Dad's computer.
Partitioned his D Drive (about 700 GB of space total) into a 50 GB "X" Drive for Win7. Downloaded it, extracted the *.iso file, ran setup.exe, and it worked fine.
He rebooted into Vista and nothing works. Keeps getting registry errors, and he can't system restore. Is this him being a moron and not being able to find it, or the computer not working at all? I'm not sure... split parents, and I live with my mom. Tried helping him over the phone to no avail. Google was just as helpful.
System restore from Win7 didn't work....

What went wrong, and how do we fix it?

So you tried running two OSes on one computer?

ran setup.exe

This is probably why. You don't install an OS while another OS is running...

You're supposed to burn the .iso onto a disc, put it in the disc drive, tell your computer to start with the disc drive BEFORE the hard drive when it starts up, and then install it in the smaller partition you created.

You most likely installed wrong. When you download the .iso, you need to butn it to a disc. Then after it's burnt, you stick it in your drive. Restart the computer and hit F12 when prompted, then pick which partition you want to install that .iso to.

if you resized the partition that vista resides on, that's a very probable cause for your issues. otherwise i'd try running chkdisk and see what's up with the partition, it seems like you have some data corruption going on somwhere. if the MBR or whatever got fucked up by win7, you wouldn't even be able to get in. another possible thing is maybe win7 tainted the partition vista resides on somehow? but i rate that as unlikely.
tl;dr: run chkdisk on the vista partition

You most likely installed wrong. When you download the .iso, you need to butn it to a disc. Then after it's burnt, you stick it in your drive. Restart the computer and hit F12 when prompted, then pick which partition you want to install that .iso to.

This is what I would say to try.

I shot the vista! But I didn't shoot the XP.

if you resized the partition that vista resides on, that's a very probable cause for your issues. otherwise i'd try running chkdisk and see what's up with the partition, it seems like you have some data corruption going on somwhere. if the MBR or whatever got pineappleed up by win7, you wouldn't even be able to get in. another possible thing is maybe win7 tainted the partition vista resides on somehow? but i rate that as unlikely.
tl;dr: run chkdisk on the vista partition

There isn't anything wrong with making the vista partition smaller afaik. Unless you mean resizing while you're in vista, though i do remember a program that resized that was on vista...

Anyway, if you wanna resize you should use a linux live CD anyway. Even if you don't use linux, there's a lot of stuff regular people could use a live CD for.

Resizing partition when there's stuff on it can cause issues, especially if the disk is fragmented and/or whatever you're resizing it with is stupid.

And having just rescued myself out of 2 days of ahh-I-can't-boot-help-me that seemed like a week, I second that comment about the live CD.