I had my Fedora 11 running for a while until recently, I added some services. Right now, it boots to grub> prompt and I don't know how to do next?

I tried to reinstall with CD, but it went to linux system from the CD and I couldn't be able to reinstall it.

Can anyone help me this out? How to boot from grub? how to remove grub? how to reinstall linux?

Thanks,

Roger