My Iphone 4S cant restore from backup and now my phone is empty!

I backed up my Iphone 4S 32G on my itunes which is installed in my windows 7. After the back up, I tried restoring my iphone to the previous backup because I was hoping that it will stop the lag in my iphone. But halfway through the restoring. Itunes tell me that they are unable to restore my phone because there is not enough space for the backup. I tried deleting and uninstalling most of my programmes in my computer. and i had 2G of space. But when i tired restoring. it sitll says that I do not have enough space. I cant uninstall anymore programmes because the rest are all nesseray Windows programmes. How much space does the iphone need to just restore??? I am not backing up. just restoring. I dont know what is wrong. How do i get abt restoring back my phone?? because now i am having an empty phone and i can get back my contacts!!!! I can reinstall the apps manually! but my iphone photots and my contacts are the most important!!