Dell OptiPlex 360 (Late 2008) - Manual (Page 92)

92 Memory Modules
7 Click the General tab, and verify that the amount of memory (RAM)
listed is correct.
8 You can also enter the system setup program to verify the new memory is
recognized by the computer. For more information on using the system
setup program, see the Dell Technology Guide on your computer or at
support.dell.com.