Hi, Ubuntu is rated as the best Linux distro. Anyway I think it is the most popular.
Linux will run fine on any socket A motherboard or newer.
A Linux computer will last 5 years, compared to 3 years for a Windows computer.
There are distributions of Linux for older hardware like Damn Small Linux, Vector Linux, STX.
azy, probably the most important thing to keep in mind with any of the newer, desktop-oriented Linux distro is that things , while generally easy to set up and use, are done differently than in Windows. There are many great information resources out there online, including the vast user communities and wikis, and just simply searching as well. My primary piece of advice is don't get frustrated because Linux and BSD can do many things that you can't easily (or sometimes at all) elsewhere.
Are you refering to mouse sensitivity? If so, the easy way (but it is dependent on what driver you are using) is to simply add an option to the Xorg configuration file. If mouse sensitivity is what you are refering to, we kinda need to know what mouse you are using and how it's configured in Xorg (list the area for the mouse, should kinda look like the following...)
#Some options here, i.e. I can use the option Option "Resolution" "800"
Perhaps the more pertinent question is how do you plan on playing CS in Linux? Wine can be a little tricky to setup, it seems to work well with non-free Cedega, but then again it's non-free.
Go here, I'd suggest giving 6.10 a spin (lots of nice new features), pick your continent, country (or closest available), then a mirror location. Download the ISO, burn it (if you don't know how, go here and follow the instructions), and enjoy! Note that the CD is a little different than the Windows XP install CD in that it will bring up a full environment (running off of the CDROM, called a liveCD, so it will be slower than when you have it on a hard drive) that you can play around with and, if you like what you see, launch the installer from the desktop.
If you start getting serious about wanting to install it, there are many great guides out there to set up dual-boot systems without needing to destroy your current Windows setup by non-destructively resizing the Windows partition to make room. Or of course you can stop back here and we'd be glad to help you through the process.