Assuming you are using the HP XP disk this is their next step:
This should retain all your data and settings. However if your data is extremely critical it would be advised to remove the hard drive and back it up first.
If the Repair Install doesn't work then you would need to do a Full Clean Install which will remove all your data while restoring the computer to factory conditions as seen here:
http://h20000.www2.hp.com/bizsupport...ctID=c00681978
Again you can remove the hard drive first and extract your data prior to reinstalling. All you need is a laptop hard drive adapter and a working desktop.
Here is a guide to that process:
http://articles.techrepublic.com.com...1-5160538.html