IBM THINKCENTRE 8123 - Manual (Page 14)

6. Some models have an optional hard disk drive mounting bracket 1 installed.
When this bracket is installed, access to some of the CRUs or FRUs inside the
chassis is restricted.
Note: There appears to be two drive bays in the bracket. However, due to
thermal restrictions, only the bay 2 at the rear of the chassis can be used to
install a hard disk drive.
See “Pivoting or removing the optional hard disk drive mounting bracket” on
page 7.
To replace the computer cover, see “Completing the installation” on page 33.
6 Hardware Replacement Guide