Problems with Mac G4

I hope I'm not repeating a question already posted, so here it goes:
I recently tried to install an Airport card (original, not extreme), into my Mac G4, but all I got when I turned it back on was a gray screen. I took the card out, but I'm still getting a gray screen that eventually has a picture of a folder with a Mac face and a qustion mark pop up. Is there anyway I can fix this without erasing everything on my computer? I was stupidly going to back everything up AFTER I installed the airport card. *stupid stupid stupid* Any help for me would e great. Thanks so much!

The icon of the folder, face, and question mark pop up after a few minutes of the gray screen and it just sits there...staring at me. I've tried restarting it, but that didn't help. It still goes from a blank screen to the icon and stays there. :-/ I was hoping it would eventually lead to something, but after 15 minutes it was still like that.

Have you tried booting your Mac from a CD/DVD?

- Nick