There are only 2 types of computer users those who have lost all their data and those who are going to loose all their data.
If you don't want to be in the first group BACKUP everything before proceeding any further. As you are saying that both Drives and all partitions are affected it is reasonable to expect the the Drives themselves are OK but the Windows XP install that you are using has been corrupted so if you don't BACKUP IMMEDIATELY the risk of loosing all your DATA is much greater.
I would suggest a External HDD mounted in a USB Caddy and copy all your Data straight to it with out any form of Compression or Encryption and then attempt to repair your system. I would suggest Super Copier to copy your Data off the system to the External Drive as it is far Superior to the Windows Copy system.
http://tinyurl.com/5mx6d2
After you have a complete Backup of your Data unplug the External USB Drive using the Safely Remove Option in XP and place it somewhere safe where it can not be used till it is needed.
Depending on what you have and what happened to this install you can try a Repair Install of XP if you have a M$ Branded XP Install Disc by following the directions provided by M$ here
http://tinyurl.com/g4bv8
If you do not have a M$ XP Install Disc but a Computer Makers Recovery Disc you can not perform a Repair Install as this option isn't supported by those Disc Types. You will have to rebuilt the system to the Original Factory Settings an then recover your Data to the Computer.
No matter what you try to do without a Solid, Functioning Backup you run a major risk of loosing all your Data so it's not worth the risk in proceeding any further.
Col
