PC100 & PC133 - What to do?

Hmm, well it depends on if you're using clsoe to 512 MB of ram. If you are then keep it, if you're only using ~300, which you probably are using at boot, then kick out the 128...But I mean, it's 100 vs 133...time to upgrade my friend

What tool do you recommend I use to tell how much RAM I'm using?

task manager

CTRL+SHIFT+ESC

performance tabe

Physical Memory, Available?

With IE7 & Outlook Express running, it says:
Total 654896
Available ~201500
System Cache 341332

Your on the ragged edge of no go. The amount of speed difference between pc100 and 133 is minuscule but adding a 256 or 512/133 in place of the 128/100 should give you a somewhat noticeable increase. Don't spend good money doing this cause you should be saving up for a four generation newer box.

T

Got it, thanks.

Addendum: anyone contemplating this should read Tom's article http://www.tomshardware.com/reviews/navigating-memory-u... specially page 15.

T

Either way will be a bust. The difference between 133MHz and 100MHz, assuming the motherboard even supports 133MHz memory bus, is going to be negligible. The difference between 640MB and 1GB, also negligible. You don't have any shared graphics memory, and have over 200MB RAM available for use even with IE 7.0 and Outlook Express running. You're not running "low" on available RAM, particularly for Windows XP. Anything more 512MB on Windows XP begins to court the law of diminishing returns, unless you are running applications that really need it (and it doesn't appear you are).

Thanks again.

I'm not looking to buy more RAM, just wanted to know if I was using what I had as well as possible.

The 128MB PC100 was off an old PC. When added, it seemed to improve performance compared to the 512MB PC133 alone.