Emergency - please help!!!.. :'(

Hi All.. Im Almost In Tears Now Because Of This Confounding Problem..

Alright.. The thing is.. I have a laptop and a desktop.. My laptop first had windows Vista home premium OS.. and the desktop has a Windows XP OS.. Now I wanted to install Windows 7 on the laptop so I bought an external HD case and copied all my data from Windows Vista [laptop] to Windows XP [Desktop].. Once my laptop had no important stuff in it I did a clean install of Win 7.. I loved Win 7.. so I decided to bring back all my files in to the laptop.. I did the same thing again, used the external case to connect HD to XP desktop and copied all the files into Win 7 HD [laptop].. I connected the HD back to the laptop and booted Win 7 up.. but when I checked the C: drive for my folder all it did was show 0 bytes and if I tried to open it it says "Corrupt or unreadable".. And yet my C: drive shows clearly that disk space has been utilized [I had 160 gb free before now its only 90gb free] .. So i know my data is there.. Its just not detecting it.. BUT WHY!!??.. :'( .. I tried reconnecting HD to the desktop to see if I could access files but now even XP is saying its corrupt and unreadable.. Its almost 90gb of memories and pictures and stuff that will never come back again.. Please help me.. I just dont know what to do..

[i dont know if it has anything to do with filesystems etc and even if it does i dont know how to fix this issue.. I definitely disconnected the HD properly every time i did the transfer so that couldnt have been the reason..no viruses nothin either..and also when I first backed up stuff from the Vista laptop onto the XP desktop all the files were accessible.. it was only after I brought them all back from win XP desktop onto the new win 7 laptop the files got corrupt and weren't recognized in either OS environment].. hope someone can find a solution..once again..thanks a lot for ur time.. :)