Do you have problem with hard disk drives (HDD) that suddenly disappears in Windows and cannot be accessed unless you reboot? This can be the answer to your problem.
Large new so called “green disks”, like 1,5 Tb and larger Western Digital and Samsung disks, seem to have problems with the AHCI disk mode in BIOS. Resulting in that these disks can disappear from Windows 7 and other Windows versions.
Check in BIOS if your hard disk drives are set to “AHCI” mode instead of “IDE” mode. If they are set to AHCI, change to IDE and reboot your computer. Your disks should now stop disappearing from Windows.