Help. Dual boot won't boot.

Just when things were going really well.
Dual booting Vistax64 and W7x64 and I've somehow screwed it up and can't boot at all.
Last night I must have done something dreadful and today I can't boot at all into either operating system and I think I may have made things worse.
I'd noticed that my small OC had returned to default. Not sure how but probably during all the frantic installing I've been doing lately. So I went into the BIOS to restore it. I then checked the boot order so I must have done something wrong in there.

When I rebooted I got a "Disk read error. Press Ctrl-Alt-Del to restart". When I did this nothing happened at all so all I could do was a hard shutdown. Since then I haven't been able to boot.
Needless to say I removed the overclock but same result
I then tried a repair install with my Vista disk and tried again-same result-disk read error etc.
Did the same thing with mt W7 7100 disk- same result.
Just now, in desperation I've reinstalled Vista. That has got rid of the disk read error but gets to the boot choice bit and just stops there. I don't get a boot choice just a blinking cursor.
I tried another repair from disk and both os tell me no problem and the pc booted normally.
I'm typing this from the Asus Express Gate OS that came with my mobo but I don't think I can do much with it.
Can anybody advise me?

Thanks, John

All you had to do probably was set back the bios to boot off the drive that contains the boot files. You probably inadvertently told bios to boot from a different drive, hence the error upon booting.

If I were you, I'd change the hard drive that is booting now and see what happens. Take things from there.

Hi torrentg, thanks for your reply.
I have 2x500GB drives so I went into the BIOS and swapped them but no joy.
Same result. Booting from the hard drive I get the Express Gate Splash plus two Asus splash pages and then a dark screen with a cursor. Normally at this point the cursor would move down slightly and I would get my boot choice Windows 7 or Vista but now it just stops there.
It looks like it's trying but cant find the boot choice.

Thanks again,John

Thanks Ted but as you can see it made no difference. I think I've really screwed things up. Can't even access my fresh Vista install. John

Not sure how to do that Ted. Do you mean take the battery out of my motherboard?
Thanks, John