Need help istalled 2GB of ram but only 512mb usable

[pb18]

Hi Guys

I have an old system which I will be selling for someone to use for basic stuff like browsing the internet etc, However when I upgraded the RAM from 1GB To 2GB it says on WEI: installed 2GB of ram but says that only 512mb is usable

system Specs:

PC specs:

Motherboard: HP NR146 SP#351067-001 Socket 478 Motherboard [MB33], http://www.ebay.com/itm/250775817842
intel P4 HT 2.60GHz & Coolermaster 478 CPU Cooler
PSU: ColorsIT 400W PSU Model (400U)
2GB DDR1 RAM (512MB x 4)
360GB storage (320GB IDE & 40GB IDE)
Case: CIT 2016 Midi tower case

please could someone help me with issue, any answers/opinions would be greatly appreciated

 

[rgd1101]

check msconfig boot advance options

 

[pb18]

check msconfig boot advance options

@ rgd1101 thanks for reply,Just done that & now when I reboot just before the Windows Boot logo the PC just restarts itself & when I go to the start up repair option i just get a blue screen saying: MEMORY MANAGENT & I can not boot into Windows 7