What program can I use to open up .gp4 files?

I was trying to open up a car using certain programs in CSM. But I could not find a Program to open up the .gp4 file. Now I can't use GP4 as I have changed the .GGP4 file to open using Slimtex. I need to know how to change them back to unknown format (Without deleting Slimtex) or use a file which opens .gp4's. Thanks for reading.

for an .gp4 file to open you need gp4builder from Lo2k (laurent) you can find that with this link: [www.realgpx.com]