OS XP Home reset on its own?

Trouble with OS XP Home edition

I have a laptop with a partitioned hard drive with OS XP Home and the other XP Pro.

This is what happened.. in the OS XP Home partition..

Everything was fine on Monday morning, but when I turned my pc back on Monday evening it did a windows scan and set everything to a default setting, and since then I can't even do a system restore.

Rebooted and went into safe mode and still can't...

*access the internet with wireless or hard wired
*save a document or copy, paste etc. without it giving me a message that I cannot link etc. I did save one doc on my flash drive after making a folder called Calendar. I have the month of June, but it will not allow me to save in the same folder all of my calendar months I have!

I scanned for viruses, but it came up with nothing? Hmmm what can cause this to happen and any way of returning the OS XP Home back to its original settings?

Oh, the partition with OS XP Pro...never changed but I do use the other one and that is where everything is!

Thanks in advance with any help you can possibly give to resolve this problem.