Well, the first thing that comes to mind is; what operating system do you use? Is it 32bit or 64bit?

A 32bit O/S cannot address more than 3.5GB of RAM. So if your graphics card takes the .5 that only leaves 3GB. Any more will not show up in windoze.

You can still, however, check that it's detected but not used. CPUZ and the BIOS should both show the total RAM. For simplicity I'd get CPUZ from here (d/l in top left hand corner, it's free) and see if it's detected, just not used.

If you are using 64bit there may be a problem (like an old BIOS or something) but we'll cross that bridge if/when we come to it.

thanks for the reply! I am using xp pro 32 bit. Can i install a 64 bit os? What are the requirements? My pc is a running on pentium d 3.0

Yeah you can install a 64bit o/s, your CPU supports it. A compatible CPU and motherboard are the requirements.

I can't give o/s recommendations, as people's experiences vary so much. Some love this and that, others hate it.

I've never used XP-64 but I hear in can be difficult to find drivers for obscure things, like webcams etc.

I use Vista-64 and have never had a problem but I don't have lots of extras (like printers, webcams etc.) so I've not really thoroughly tested it.

thanks The New Normal, you'd been a big help!