My answer is based on these assumptions:
1. You did not kill your Asus MB by overclocking it.
2. You do not want to lose data on your original HD/partition and are thus not willing to format it.
3. You want your original HD to run the same OS it did before the crash.
4. You own the CD's necessary to re-install your first OS.
First, if you want to run a dual Windows OS system w/ XP you need to have a working copy of the pre-XP system installed first. So, if you've installed XP on top of the crashed version of your old OS you will need to uninstall XP to setup a dual OS system.
Second, it sounds like there's a possibility that some data was corrupted during the crash. If this is the case I'd run an extensive disk doctor or scandisk on your HD to check for errors.
Finally, now you can re-install/repair your first OS and then install XP. I believe that microsoft provides an explanation of how to setup dual OS systems in their knowledge base. Consider it required reading.
http://support.microsoft.com/default...b;en-us;306559