If you want to try to rebuild the Dell we can help here. Just say so. I will move it to the hardware section & we can take you thru the process.
If those drives are in good shape & you have the Dell case (by which I am assuming is a functioning mobo etc.) you might as well use the drives in there; or at least two of them while you use the third externaly.
If you put the Dell drive back into the Dell case you should be able to use the Dell recovery disk to reinstall XP.
As to online storage I personally know nothing except via google:
http://www.ibackup.com/features_storage.htm
You might want to start a new thread for suggestions under the Other Software section.