Finding out "exactly" what RAM is appropriate for your machine has been made easy by "Crucial".
They feature a scanning type utility at their website that you can have scan your machine.
The Results will recommend exactly the type of RAM your machine can accomodate.
Crucial will also offer to sell you their RAM modules.
I like Crucial, which is a good product, but sometimes I don't like their prices.
I also like Kingston and PNY which are also good brands.
If you are lucky and have several electronic stores near-by, watch their advertized Sales.
Sometimes you can get a "real bargain" locally.
For "Online" purchases, I like:
http://www.newegg.com
http://www.tigerdirect.com
http://www.zipzoomfly.com
Once you've determined what you need, by using the utility at Crucial………. Shop around.
http://www.crucial.com/systemscanner/
Note: If your machine requires PC2100 or PC2700, you can use PC3200 which is "backwards compatible" and usually considerably cheaper.
Reason, They just aren't making PC2100 or PC2700 much anymore, whereas many newer low-cost machines use PC3200……… so the supply is greater, at least for now.
If your machine uses PC4200 or above, you must buy the precise replacement type.
Fortunately, PC4200 is almost standard now in brand-new machines, so the price is reasonable.
If Crucial tells you that you need PC800…….. it "may" be possible to use PC3200 in some specific circumstances.
Otherwise, just hope that you don't need PC800 as it (RDRAM) is expensive.
If you machine runs on PC 100 or PC133, you can use either without much noticeable difference.
RAM always runs at the slower rate when more than two speeds are present in a machine.
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About "buying a Disk".
Does your machine have a CD-Writer, and do you have Easy CD Recorder or Nero, or similar installed.
I can't remember what your machine actually looks like. Sorry.
Buy CD -R. and "Don't buy" CD-RW.
CD -R is about $0.15 US per disk, whereas CD-RW is about $0.80 US per disk.
And I really don't know anybody who actually "uses" CD-RW, particularly because it's not all the good, and it requires more expensive, resource intensive, and combursome software to record CD-RW.
Best Regards