access to devices

hi, Im using device IO control to get access to the physical disks on my machine. So far i have a program to access the first 3 physical disks, but when i come to access the 4th my program stops working?!!? I have 4 physical disks in my machine so i was wondering if it is a case of device io control only allowing access to 3 physical disks at a time? surely this cant be right as im closing the handles on each disk after im finished?

Im sorry this is a bit of a random questions and i understand if no one has any idea what im talking about but in this case im not sure that posting my code will help any

any opinions would be welcomed?

Are they numbered 0 to 3 or 1 to 4?
If it's the former, and you're trying to access number 4, then yes it will fail.

Also "doesn't work" doesn't help!
Go through your code and add verbose error checking and reporting of any and all error status returns, and then post relevant code and error messages.