Garry's Mod not seeing new resolutions

[drake90001]

I just got a new monitor, resolution of 1366x768 (Its wide screen). But when I start up Garry's Mod, it goes back to my old 1024x724 or whatever. Do I need to do something? I have an ATI Radeon HD 4350. Dell IN1920 monitor, its 15.5 inch's or something. Windows XP (the MOST stable version of Windows in my opinion, I do own my self a copy of Windows 7, but I need some more ram.)
ON-TOPIC; I can play L4D2 in my new resolution, but not Garry's Mod -.-;

[b]EDIT:[/b] Ohhhhhhh, I got it. I had to change my aspect. Silly me.