> The error message that is displayed "error loading operating system".
If I remember my days using Partition Magic, this is a Partition Magic error (unless you saw a big 'ol "grub" or "lilo" logo before the error message appeared). This suggests to me that, despite all efforts, you still have Partition Magic on your MBR. The Redhat install disk should be able to fix this by simply writing over the MBR. Make sure that when you are asked by the install disk where to install lilo/grub that you chose the MBR.
> I now intend to do a complete backup then re-install the OS again.
That may not be necessary. You can make your computer run WinXP just fine without reinstalling anything, just do as Brianstech said. If you plan to re-install WinXP and Linux, install WinXP first and then Linux. Installing WinXP will also overwrite the MBR (another way to get Partition Magic outta there). If you are just reinstalling Linux, be sure to read the installation directions carefully in case you missed anything important the first time.
> For example, Drive C was 40, then 30 + 10. If I delete the space allocated for 10 GB, would my drive C go back to 40?
No. If you delete the 10GB Linux partition you will be left with a 30GB Windows partition and 10GB of unallocated space. To make that space appear on the C drive (as seen in windows), you would have to merge it with the Windows partition (i.e. with Partition Magic or fdisk) to get a 40GB Windows partition.
If you are planning to reinstall Linux, you probably do NOT want to merge that 10GB unallocated space with the Windows partition. Rather, leave it be and let the Linux install disk use it for the new Linux partition.
> Please don't quit there, we all need to stick with it longer than our first attempt.
Indeed. It took me more than one try to get Linux to boot properly on my machine, and I've dealt with numerous problems after that. But in the end you get rewarded with free software, more and better features, less bugs, more stability, etc, etc. So don't give up!