iPhone 3 G

I am unable to access iPhone because:

On my screen I have three layers, top layer is the "keypad", second layer is "Nothing to Undo", third layer wallpaper picture.

I first tried turning the phone off but the "slide to power off" will not move. So cannot turn phone off.

The SIM card I took out and put back in.

Would appreciate any suggestions on getting this phone back to work.

Thank you.

Sadie