Different methods to identify the RAM are
From the POST Messages – As PC boots it generates various messages about system components including the memory. Pressing the ‘Pause’ key, will halt the display so you can read it.
Ask Operating System – Windows XP can tell RAM in PC by Clicking Start >> All Programs >> Accessories >> System Tools >> System Information. This will open a ‘System Information’ window and in the summary it will tell you the total amount of RAM recognized in PC.
Use Third party tools – System information or diagnostic tool available can be used to tell the RAM installed in the PC
Open the Case and Read the Labels – The RAM stick(s) have a label giving appropriate information about the size, speed, manufacturer and possibly some warranty information.