Hello Shimminb, and welcome to Seven Forums.
In your case here without any way to fix the accounts normally, you might consider doing a repair install
while logged in (not in Safe Mode though) with the built-in administrator account in an attempt to have the user accounts restored with Windows 7 during the repair install. If it does not, then you should still have the C:\Users\(user-name)
folders for the accounts that you can copy the users accounts files to backup from. If not, then see step 17
at link above to find the user files.
Hope this helps,