back it up prior to doing a fresh install.
A "fresh install," (or installing the OS on an external and booting via FW) which will lose all third party programs and cause a much bigger headache, is not necessary. I suggested an A&I. It is, of course, preferable to have a backup when doing this, but it will most likely come out alright.
Do you have an external disk and does it have a full backup?
If the OP had a "full backup," either in the form of a bootable clone or TM -- something I wouldn't ever think of not having -- then a restore from the date before this happened would take care of the problem. I assume there isn't one, since it probably would already have occcurred to the OP to do this.
This would allow you to use Disk Utility on your install CD/DVD.
I think the problem may be too severe for that. In most cases, whatever the OS, an A&I, reinstall, not erase and install (Snow Leopard) or restore is what is needed.
Message was edited by: WZZZ