My mouse/cursor has disappeared. HELP!

When I ran Garry’s Mod, a joined my favorite DarkRP server, and I realized my window was around the game. I took that off by going into Options, then in the Video options. It took a minute to go from a black screen to the actual game, when it was done loading I was playing in full-screen. When I went into my options again, my cursor has vanished. I’m playing on a Windows Vista. It works fine on my desktop, like when I click the short-cut and it opens up to the main menu, the cursor isn’t there. So I can’t click anything, such as Single Player or Multi Player. Please respond!