You can perform a server reinstallation. You will lose any customizations you may have made, such as add-ins, software installed or configuration changes made outside the console, etc. but your data (and normally your backups) will be preserved.
To perform a server reinstallation: Insert the WHS installation DVD and reboot your server. If asked, choose to boot from the DVD. On the hardware discovery screen, make sure all your hard drives are connected and visible. If they are, when you're asked what kind of installation you want to perform, you should be given the option of a server reinstallation, as well as a new installation. If one or more drives isn't visible, then you'll have to supply drivers for setup to succeed with a server reinstallation. If no drives are visible without supplying drivers, then you will need to supply drivers at the hardware detection screen, and then again just after the server reboots into text mode setup (at the "Press F6" prompt).
If all your drives are visible, and you aren't given the option of a server reinstallation, STOP. Get back to us, and we can help with alternative methods of recovering your data and getting WHS reinstalled.
If you have an OEM product such as an HP MediaSmart Server, you should consult the documentation you received with it, as procedures for performing a server recovery (the OEM equivalent of server reinstallation) will vary.
I'm not on the WHS team, I just post a lot. :)
