WINXP PRO BACKUP HEADACHE

i used the windows backup utility---ie i did a right click on my hard disk-went to properties, chose the tools tab then the backup now button---i backed up all the information on my computer through the network to another networked machine----my computer was running in windows xp pro sp1-- i backed up the data on a machine running win xp pro sp2---after backing up i went ahead and did a complete format of my hard disk drive and reinstalled windows but this time i reinstalled win xp pro sp2---after i was thru i tried restoring the back uped data but all i get is the data is not recognised--it is refusing to restore my back up---this back-up contains very usefull patients data since we run a clinic--does anyone know of windows having incompatibility issues with the backup???? should i roll back to my old win xp pro sp1---or is my back up corrupt--anyone with any ideas of what i shud do???? Please Help.