eek. tell me you didn't reformat the hard drive!! i guess you have a minimal chance of getting your data back...but let me stress...minimal if you reformatted. !! if you didn't reformat you may have to activate the disk. I'm sorry i can't tell you how to do this because i just has surgery and i can't get to my xp computer

. I think (stress think) that it is start, control panel (make sure it's in the old fashioned mode), administratoin tools, computer management, storage, disk management, go to the hard drive your information is on, and right click it. (this should be disk 0 if it's your only hard drive). Make sure the disk is activated (again, it should be, considering your primary partition is on that hard drive..i think) then make sure the partition with your information on it is active and has a drive letter and stuff. see what xp tells you about your partition there. if you reformated...it's not quite so simple...your in deep crap there. Also..if you reformated i'd suggest waiting for instruction from now on instead of doing what you think sounds like it will work. I only say this because you are really in a tight spot if you reformated to one big partition. Please don't take what I say as rude, because it's not meant to be...just very blunt. Anyways...welcome to timo, if you follow our directions 100% we should still be able to get some of your information off there for you.
now..if you reformateed to one big partition, things get more difficult. I'd suggest going out and getting a new hard drive. If you want a nice big one, go for it, it you want the cheepest because you don't plan on using it..that works fine too. Take the new drive, and install windows xp to it. You want to make sure, when you start your computer, to start this installation of xp. what I'd do is this. Remove your old drive w/ all the info and put in the new one. Install xp and once your done install all your data recovery software. Next click my computer, folder options, the second tab (i forget the name), and make sure you can see all hidden and system folders. Next go back to my computer and double click c, look for your boot.ini file and it should look something like
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOW S
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Micro soft Windows XP" /fastdetect /NoExecute=OptIn
change windows xp in the fourth line to good windows. (odd yes, but important)
The reason you wanna do this is because simply having xp running on the drive your files are on, you risk them being overwritten by xp. I really would suggest right now, printing this out, getting another hard drive, and installing xp on it (i'd say atleast 10 gigs will do it if you have one lying around). The more you run the computer off your current hard drive, the less likely you are to recover those files.
Let us know if you did reformat the partition or not and if you did, when your ready with another hard drive and a full install of xp.