Listen Server won't start.

I used to play garrysmod all the time and me and my friend would use a listen server to play. When the big update came my computer wouldn’t run it very well so i stopped playing for a while till i just got a new computer.(I know it happened a LONG time ago) Now with my new computer it starts to load the server, sits for a while, then goes back to the start screen. I tried refowarding the ports and that didn’t help so i tried downloading a dedicated and that wont let me join. So if anyone can help me with either dedicated or listen server that would help.

P.S. I’m runing Windows Vista Home Premium 64bit if it makes a difference.