iaStor.sys belongs to the storage drivers for the controller on the motherboard.
BUT, it also rears it's ugly head in a BSOD if you are infected with some variants of the TDSS rootkit.
There are other, less likely causes, but these are the 2 most common.
Try this free tool to see if you are infected with TDSS:
How to remove malware belonging to the family Rootkit.Win32.TDSS (aka Tidserv, TDSServ, Alureon)? (it'll run in Safe Mode). If you are, and it still doesn't boot, you're in for some gyrations to get it to work (running multiple virus removal tools and multiple commands with bootrec and Startup Repair - that work in most (but not all) cases.
See if you can update the Storage drivers in Safe Mode (some installers will allow this) - and try the storage drivers from
http://downloadcenter.intel.com to make sure you get the most current version.
We can troubleshoot this further, but if it's the rootkit you're best off with wiping the hard drive and reinstalling Windows.
To do this it's essential that you:
- backup your stuff (and scan it with an antivirus)
- find the restore disks for your system (not the restore partition on the hard drive)
- wipe the drive (to include all freespace) with either DBAN or KillDisk (both are free with a Google search)
- install Windows.