RAM not being fully recognized, and not running full speed

[HaLo2FrEeEk]

I have 4 Gigs of DDR2 PC-5300 RAM. 2 sticks of it are A-Data, they advertise to run at 667mhz, I believe this is them:

http://www.newegg.com/Product/Product.aspx?Item=N82E16820211061

The other 2 are PNY that also advertise on the packaging to run at 667mhz, I think this is them, only mine have heat spreaders:

http://www.bestbuy.com/site/olspage.jsp?skuId=8221453&type=product&id=1166236338366

There are 2 problems, one is that Windows XP Media Center (x86, so 32-bit) is only recognizing 3.25 gigs in system properties. The other thing is that when I run CPU-z, it tells me that the RAM is only running at 335mhz average. It reports the PNY sticks as running at 333mhz and the A-Data running at 400 mhz. Both, however, say they are capable of 667mhz. Here is a picture of my mobo's RAM slots:

http://claninfectionist.com/images/misc/untitled10.jpg

And one of the RAM installed:

http://claninfectionist.com/images/misc/untitled11.jpg

I just recently installed XP Media Center over Vista, but Vista (I had 64 bit) recognized all 4 gigs, though it also reported them running slower than 667. Is there anything I can do anout this or should I just stop complaining that I'm losing a few hundred megahertz?

Thank you in advance.

EDIT: Here is a picture of all the parts in my computer, I didn't have one of just the RAM modules, but you can see them:

http://claninfectionist.com/images/misc/untitled4.jpg

 

[mailpup]

You might not have anything wrong. 32 bit operating systems, whether XP or Vista, will not recognize the full 4GB of RAM, a 64 bit OS will. The 3.25GB is about right.

Keep in mind your RAM is DDR2. DDR is double data rate so it will be reported in the BIOS and CPU-Z at about half of its rated speed.

 

[HaLo2FrEeEk]

So why does one 667 stick (well, 2, the A-Data one's) report at 400 mhz?

 

[mailpup]

Perhaps they are overclocked (inadvertently) or it is actually DDR2 800.

 

[HaLo2FrEeEk]

You know, it could very well be DDR2 800, but I bought them almost a year ago...so idk. I remember telling one of my friends something about 800...I might have meant DDR2-800...that would make sense. Ok, I'm sated now. But another question...does the slower reported speeds mean that the actual RAM is running slower or is it running what it's supposed to?

 

[mailpup]

It is running as it is supposed to.

 

[HaLo2FrEeEk]

Thank you for your help!