Add the NoDrives DWORD value (this value defines local and network drive visibility for each logical drive on the computer. All drives will be visible as long as this value's data is set to 0) under the following Registry key:
HKEY_CURRENT_USER | Software | Microsoft | Windows | CurrentVersion | Policies | Explorer
NoDrives - The DWORD Value is derived from the following...
The "NoDrives" value uses a 32-bit bitmask to define local and network drive access for each logical drive in the computer. The lower 26 bits of the 32-bit word correspond to drive letters A through Z. Following the table below, enter the decimal number corresponding to the drive(s) you want to hide as NoDrives value data. When you right-click on NoDrives and choose Modify, make sure you select Decimal base, not Hexadecimal...
A: 1, B: 2, C: 4, D: 8, E: 16, F: 32, G: 64, H: 128, I: 256, J: 512, K: 1024, L: 2048, M: 4096, N: 8192, O: 16384, P: 32768, Q: 65536, R: 131072, S: 262144, T: 524288, U: 1048576, V: 2097152, W: 4194304, X: 8388608, Y: 16777216, Z: 33554432, ALL: 67108863
For example to hide drive A and drive D, you would add 1 (A) + 8 (D) which means the Decimal value should be set to "9". To disable all the drives set the value to "67108863".