lol ! how can a folder disappear like that XD!
1 Ur hard disk is broken ?
2 Ur antivir had find a virus in that folder and had moved all in quarantine ?
3 A member of ur family thought u played to much and deleted the game?
4 U have changed many times the gta IV directory? (i mean by reinstall to repair smth) edit: if u did that search better maybe u will find
5 U got hacked ._. (unprobably)