Ram doesn't register full amount??

[sirzune1]

I just inserted an identical 2GB ram module in a Lenovo ThinkCentre computer. It actually worked quite fast with just the 2GB module, but I happened on an identical machine and took out the ram and put it in the one I'm using. It only registers 2.99 GB ram. How can that be when this machine can take 8GB ram? Any solutions? This may be helpful:
Time of this report: 11/19/2011, 13:43:20
Machine name: 2PZ-OFFICE
Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 3 (2600.xpsp_sp3_qfe.101209-1646)
Language: English (Regional Setting: English)
System Manufacturer: LENOVO
System Model: 6072A81
BIOS: Lenovo ThinkCentre BIOS Ver 2RKT38.0
Processor: Intel(R) Core(TM)2 Duo CPU E6550 @ 2.33GHz (2 CPUs)
Memory: 3062MB RAM
Page File: 532MB used, 4414MB available
Windows Dir: C:\WINDOWS
DirectX Version: DirectX 9.0c (4.09.0000.0904)
DX Setup Parameters: Not found
DxDiag Version: 5.03.2600.5512 32bit Unicode

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DxDiag Notes
Thanks

 

[IAntDemo]

most likely because windows xp pro sp3 only accepts upto 3gb..

not 100% sure, what about if you check in the bios

 

[xDrive]

Only Windows xp pro 64-bit can hold up to 128 GB, any other version are 32-bit and only hold up to 3GB as stated by -invent-, so go to control panel and click on system and check if you are running win xp pro 64-bit or a 32-bit, hope this helps

 

[FlightSimBoy]

Most common issue with only 3 GB showing up is a 32 bit (x86) operating system... You'll want to upgrade to a 64 bit (x64) operating system if you want to use 3 or more GB of RAM...