I just put it 2 new 1GB memory sticks where my former 512mb sticks were.
The former sticks were 512MB PC2-4200's.
The ones I put it are 5300's and are both the same make and brand. Identical...
When I run CPU-Z it shows that I'm still in single channel... Before with my former memory sticks it showed dual... Now when I throw the former ones in there it will remain single...
Anyone know how I would go about going back into dual channel? Hopefully with these new memory sticks.
Thanks in advance.

Here are some specs if they would help.
Motherboard
Manufacturer: Micro Star International
Model: MS-7248R

Processor
Intel Pentium D 805

New Memory
2x 1GB PC2-5300 Hyundai Electronics

BIOS
Phoenix Technologies, LTD
Version: W7248AG2 1.0K

Video Card:
ATI Radeon HD 4550

Ensure that you put the modules in slots having the same colour. Dual channel slot pairs are usually colour coded. If not, then check your mobo manual to determine which slots constitute the pairs.

Yeah they are both in the only slots I have. So they match perfectly

did you check memory compatibility, and that your dimms will accept 1gb modules?

A scan on crucial tells me this...
"Each memory slot can hold DDR2 PC2-5300,DDR2 PC2-6400 with a maximum of 1GB per slot.*"

okay try a different program other than CPUZ, and check your bios to see if it is telling you the same. it is possible (and happens) that CPUZ is mis reporting your memory status.

I wouldn't think so, because it's saying I have 2GB of ram, but it doesn't feel any different from when I had the 2 512MB of ram in... It's like I still have 1GB and 1 stick isn't getting picked up...

You probably wouldn't even notice the performance difference between dual channel and single channel operation modes. It can be tough to see any difference even with benchmarks on older systems, simply because the platform(s) do not have enough performance to benefit from the increased bandwidth of dual channel.

If your computer still feels slow, it's probably something else.

However, the memory should still be running in dual channel regardless of any tangible performance benefits. Check the BIOS to see if perhaps something is improperly configured. Make sure all the voltages and timings are set correctly.

I concur with what metal said, memory status is often misreported with various software programs. the performance boost from dual channel is 10-15% overall , but only in resource intense use. did you try reinstalling CPU-Z or a different program?