moving hard drive to new machine : can't get past grub

[P. George]

i have a redhat install from another computer that i'm trying to get to 
boot on different hardware.  i don't want to have to set everything up 
again from scratch.  a LOT of tediosity went into getting it "just 
right."  i'm sure you can relate/empathize.  ;)

so, here's what happens:  i boot and get to the grub gui.  i can see my 
install in the list.  i double-click it.  the screen goes black and the 
machine reboots.

how can i remedy this situation?

thanks.

- philip