URGENT!!! Okay I admit, I messed up! Help?

When I was like nine or something my friend called me and told me to go on www.123games.dk.com or something like that and to click on a link that said 'y games'. obviously i didn't know what that meant and a bunch of p/o/r/n games showed up and okay, I played them. I only did that cuz I thought it was funny then I stopped and never did it again. My mom caught me on MySpace and now I'm screwed! Should I tell her? It was a long time ago so I don't know if it matters anymore but I feel so guilty! My mom would go ballistic if I told her and I'd never be able to use the computer again but the guilt builds inside me and is making me be-yond crazy! HELP!