@Robert-Jubeck I think ACID can't read from or write to your hard drive because your windows user account doesn't have sufficient permissions to do it for the currently selected directory. It should work if you start ACID as an administrator (right click on the program icon and then click on the corresponding entry). Perhaps it makes more sense to use a different directory, such as the user directory.
I tried your directory change suggestion with no luck. When I first open Acid, I get a message that my temporary directory is getting low on space and that I should free up room on my C drive. If I hit ok in the box showing, the program will open, but when I try to open a project the error message of not having enough disk space pops up.
@Robert-Jubeck Ok, can you go to the location of your temp folder, make a right click on it, then click on properties, then go to the Security tab? There should be a list of users who can access this folder, for example SYSTEM and Administrators. Your Windows user should also be listed there and should have Full Control checked (and all other permissions). Is this the case?
@RYAN-BHAWANIDIN How big is your drive? Im under the impression that the drive might be too big and ACID cannot handle this. Maybe it's old code that checks the drive size and then it returns a negative number or something. In that case only creating multiple smaller partitions on your drive would help.