This behavior can be caused by severe fragmentation on your hard drive.
If you're running Windows 7, it does not de-fragment your hard drive automatically like Windows 10 does.
The solution could be to run a Disk Defrag on your C drive. You can also run a Disk Check to check for any bad sectors.
A quicker workaround though would be to go to the System Settings in AGi32 and change the location of the Working Files.
Go to Tools > System Settings
From here go to the File System tab and change the Working Files directory by clicking on Browse and set it to C:\Temp.
Restart AGi32 and clean out the old file location. Files should open normally now.