Reading only half of RAM

[Gorilla]

I seem to be having a strange issue with my computer. I have a 1gb stick that the computer will only read as 512mb for some reason. If I add another, say 256 stick it will read the 256 as full and still only the 1gb as 512. (So 768mb total) I know the stick is 1gb as it works fully in my friend's computer. Perhaps I have something set wrong or such. I'm pretty new to computers and I know my machine is kind of old. I'll put whatever stats I can find below, though I'm not sure what might be needed. Any help or suggestions would be greatly appreciated. Thank you.

Compaq Computer
Presario 6000 (6320?)
AMD Athlon XP 2000+
1.67 Ghz 480mb RAM (currently reading only 480 of a 1gb stick)

Ran a Crucial system scan on my memory and this is what I got:

Currently installed memory:

512MB
EMPTY

Each memory slot can hold DDR PC2700,DDR PC3200 with a maximum of 1GB per slot.*

• Maximum Memory Capacity: 2048MB
• Currently Installed Memory: 512MB
• Available Memory Slots: 1
• Number of Banks: 2
• Dual Channel Support: No
• CPU Manufacturer: AuthenticAMD
• CPU Family: AMD Athlon(tm) XP 2000+ Model 6, Stepping 2
• CPU Speed: 1665 MHz

Keep in mind that although it it saying 512mb, it is a 1gb stick in that slot.

Thanks

 

[pimpom]

Some motherboards can properly use only so-called single-sided memory and cannot fully utilise double-sided ones. Count the number of chips on your RAM stick. Are there 16 chips (8 on each side)? If so, see if you can borrow a 1GB stick with not more than 8 chips on it and try it on your computer.