I've just had a lot of hassle with grub being unable to work in a 
mixed SATA / PATA system. In the course of sorting it out (by using 
gag[0] in the MBR to start lilo in the Linux partition) I've come 
across a couple of superb rescue disks which I thought I'd advertise 
for those in trouble:
The first is Gujin, extract from my wiki [1]:
Gujin is a brilliant piece of software which runs from a floppy or 
bootable CD and finds every bootable system in your hard drives. It 
then gives you a menu of them all and you can boot any of them. Great 
if you've hosed your MBR or LILO config, or if grub won't boot your 
system because you have a mix of SATA and PATA drives (that was my 
issue).
The second is the System Rescue CD [2] which has all you need to run 
gparted, etc etc.
HTH, Peter
[0]
http://gag.sourceforge.net/
[1]
http://www.salisburys.net/PetersNotes-TW.html#%5B%5BGujin%20-%20a%20find-and-boot%20utility%5D%5D
[2]
http://www.sysresccd.org/Main_Page