must have an nvidia chipset on the motherboard
That would be my guess.
Splodge, this can happen, because SATA drives are hot-swappable, they are therefore a removeable device. As the system drive obviously cannot be removed whilst Windows is running, most people just ignore it.
It's frequently seen on a motherboard with an nVidia nForce chipset. If this is your situation, it can supposedly be corrected with an edit to the Windows Registry. Some people avoid altering the registry, if you do so, be aware of the risk of something going wrong, back up the registry before making any changes.
These are the instructions provided:
"If you have a Nforce4 Based Motherboard and your sata drives are showing up in Safely Remove Hardware, this registry hack will allow you to fix it.
1. Click Start -> Run
2. Execute regedit
3. Navigate to
4. Click Edit
5. Select New > DWORD value
6. Name this DWORD: DisableRemovable
7. Double click this new DWORD and set its value to one (1).
8. Close Regedit and reboot
This works on the Nforce3 also and the registry line may be HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\nvatabus"