HW = HardWare ...
hdparm - get/set hard disk parameters
hdparm [ flags ] [device] ..
hdparm provides a command line interface to various hard disk ioctls
supported by the stock Linux ATA/IDE device driver subsystem. Some
options may work correctly only with the latest kernels. For best
results, compile hdparm with the include files from the latest kernel
for eg /sbin/hdparm -d1 /dev/hda will set dma to "on" for the primary master hard disk (if the hdd supports dma). Direct Memory Access will speed up accessing for the hard drive.
Have you checked to see what processes are running?
Have you checked www.mjmwired.net
for hints how to tweek RH9?
More advances OS's will probably be able to fit better with newer hardware - HW advances have been factored into the design.
I'd suggest you look at:
... and make up your own mind. Otherwise you'll just end up getting the prejudices of whoever. Everyone has their favorite. There is a tendancy to get a tad fanatical about the particular distro one favours. Basically, linux is so varied that you are likely to find one totally suited to you. You tend to get the idea that it is "best" for everyone else too.
Here's a basic breakdown, sticking to free distros:
Fedora Core and OpenSuSE are the big-boys. These are "complete" binary distros. You will want to tweek them after install - for eg. install the i686 version of the kernel. (Probably one of the things you need for RH9 too.)
The main plusses is that they contain everything you could need, and are easy to install, and they are backed by strong commercial companies.
Debian (by Deb and Ian...)is a numero-uno distro but is notoriously unfreindly to install. There are many distros based on debian however. Ubuntu, for example, is probably the most popular desktop distro around, and is much easier to install and configure.
Debian is as complete as you want it to be. Ubuntu comes on just one CD ... which means you will be installing a lot of stuff after the initial install. (It still comes with more than windows does though.)
Slackware (mentioned) is pretty source oriented. It is a total uggerbay to set up - but it tends to be worth it because you end up with exactly the correct distro for you and your hardware and the skills are generic to all linuxes. You'll see the slackware folk around here are often the ones with the solutions. Slackware is also one of the oldest distros.
Gentoo is similar to slackware - only easier to install and configure. It takes longer... but is reputed to be the fastest as well as the easiest to install.
Yoper - dosn't make the standard lists. It is based on debian, but is optimised for i686 processors. Famouse for it's speed. I've included mostly because it is local (to me, NZ).
In the end - use the distro favored by the guru freind who lives closest to you (or the one showcased at the locak LUG install-fest.) Then you are garanteed good support.