Lenovo Thinkpad Edge 6 Gb Ram Only 1.75 Usable?

I just got a used laptop yesterday with Windows 7 Home Premium and it says it has a total of 6gb ram but right next to it, it say only 1.75 usable. I really need all the ram for some applications. I have updated the BIOS, updated Windows, unchecked the max usable ram in the Resource Monitor section. Someone help me.

What's the reported memory in Task Manager? Is your Windows 64 bit?

It says there's a total of 1790 Mb of Memory and yes it is a 64 bit.