RAM DDR PC2100.. mixing speeds pc2100, pc3200

Hi ppl,
i have scanned my system as you can see the report below..
my system is slow and i want to run it like a lightning..
Could you ppl please tell me what are the things i should be doing?
my major doubt is my current installed mem says it is DDR PC2100, can i use DDR PC2700 or more.. what is the difference between this? "can i use one slot for pc2100 and another for pc2700.."
Thanks
....
Your Crucial Scanner Results Standard VIA KM266 Specifications

Currently installed memory:
256MB
DDR PC2100
EMPTY

Each memory slot can hold DDR PC2700,DDR PC3200,DDR PC4000 with a maximum of 1GB per slot.*

*Not to exceed manufacturer supported memory.
Maximum Memory Capacity: 2048MB
Currently Installed Memory: 256MB
Available Memory Slots: 1
Number of Banks: 2
Dual Channel Support: No
CPU Manufacturer: AuthenticAMD
CPU Family: AMD Athlon(tm) XP 2000+ Model 8, Stepping 1
CPU Speed: 1679 MHz
The name of this model may not exactly match the model description of your system, our system scanner could not identify a specific model name when evaluating your computer. However, it was able to identify the motherboard your system utilizes.

 

Well you certainly can't put them in the same slot!

When combining memory modules of different speeds the whole memory runs at the speed of the slowest.

256M is too little for Windows XP

Most ordinary users find little benefit above 512M (=2 x 256)

Gamers and serious photoshoppers find 1G plenty.

A few diehard gamers with massive screens and other stuff need the full 2G

 

Yes you can mix and match, but it will default to the lowest speed installed, so it's not really worth doing unless you have no choice - although more RAM is always good, especially when you have a barest minimum (for XP) 256 like you have.

DDR Ram is expensive compared to DDR2, and adding 2 x 512 MB, which is what you really need for XP, is likely to cost more than the 2 x 1 GB sticks I just bought for this machine.

A lot of the older boards don't fully support DDR 4000 (or 1 GB sticks), so I'd choose 2 x 2700 512 MB sticks to be on the safe side and remove the 2100 stick.

There will be a noticeable jump in performance with 1 GB of RAM installed, but if you can find some 1 GB sticks that are compatible with your board - there will be little or no difference in performance, so don't bother with 2 GB.

If funds are tight, just bung another 256 MB stick of DDR 2100 in

 

..... to clarify the 1 GB or 2 GB RAM installed, what I meant was.....

If you upgrade to 1 GB and notice the big jump in performance that you should, then don't expect a big jump, if you further upgrade from 1 to 2 GB - it won't happen, and you'll not notice any difference, apart from the page file increasing in size :major

 

Promises Promises

Kinda depends what you are using the pc for and also what if any memory is given to the graphics sub system.