Re-installation of OpenSUSE11

I have installed OpenSUSE11.I have Windows xp SP2 also.But because of ATI driver corrupted only white screen is appeared after logging in.So I want to repair it by using bootable DVD of OpenSUSE11.I don’t know the steps to be followed and what are the effects of re installation.As I have configured kinternet,pidgin etc.Do I need to re-configured them.Also I have my data,files will this deleted after re-installation.Also I have mounted windows drives what will be the effects on this?

You shouldn’t need to reinstall.
You can boot to runlevel 3, by typing a 3 in the options box in Grub, login as root and type:

sax2 -r -m 0=radeon

that should go back to default (iirc) radeon driver for Ati. Then type reboot.
If everything went well the desktop should appear after the reboot.

If you still want to reinstall, take care of not to format your /home partition but just mount it during installation. That way you’ll keep all your files and settings but those regarding mounting windows drives, which you add to mountpoints in the partitioner during installation also. Double check you are not formatting anything you want to keep.

If the problem was with the proprietary ATI driver, a reinstallation will not help and is not necessary. Try using the open-source driver first instead (per @JopSway’s post above). If you need the ATI driver after all, the howto is here ATI - openSUSE. Be sure to look at the compatibility list and Express issues before doing anything.