This patch for 9625 still seems to work with 1.0.9746.
However, the installer now does a test to see if you're running Xen and refuses to continue if you are :-/. Tried the expert mode and it didn't give an option to continue there either.
For the desperate here's what I did to get it going for now (your mileage may vary):
1) Extract and patch kernel with the xenrt patch
2) Boot into a non-xen environment and install the patched version (via NVIDIA-Linux-x86-1.0-9746-pkg1/nvidia-installer)
3) cd NVIDIA-Linux-x86-1.0-9746-pkg1/usr/src/nv (the stuff you extracted)
4) In the Makefile comment out (#) the line "@if ! $(CONFTEST) xen_sanity_check full_output; then exit 1; fi"
5) Build the kernel module and install it
make SYSSRC=/usr/src/kernel/<insert kernel version> module
cp nvidia.ko /lib/modules/<insert kernel version>/kernel/drivers/video
depmod -a <insert kernel version>
Hopefully I didn't miss anything. I did try to run the regular installer under Xen before doing manual compilation, so it might be best to do that anyway in case it generated the Makefile.
I hope this doesn't indicate an nvidia don't care about Xen at all.
Thanks again to JaXXoN for the patch.
EDIT: My system is FC6, so if the source and module folders differ on your distribution you'll need to modify the commands above.