[Windows XP Mouse Acceleration]
Mouse Acceleration is perhaps the most important factor to good mouse control. While it is all preference, the key advantage to disabling mouse acceleration is consistency in movement. With mouse accel on you will notice your mouse movement will start slow and then speed up, only to slow down again. It is consistency in movement that is key to good control. It is highly recommended to turn accel off. However, even after un-ticking “Enhanced Pointer Precision” in your Windows mouse options, mouse acceleration can still find itself locked in the XP system. The easiest way to fix this is to install CPL Mouse Fix.

This “mousefix” will remove all mouse acceleration from your windows registry. I would not advise using this fix unless you are absolutely sure you want to disable mouse accel, as adding anything to your registry can be quite the pain to undo.

[Windows XP Mouse Speed]
Windows Classic View: Start -> Control Panel -> Mouse.
Windows Category View: Start -> Control Panel -> Printers and Other Hardware -> Mouse.

Another setting that must be examined is Windows mouse movement speed. Selecting “Pointer Options” from the Mouse tab menu, notice the bar at the top right under “Motion”. This bar dictates how fast (or slow) your mouse motion is. This can have a direct effect on your in-game sensitivity. If you have very low Windows speed, you will probably need a very high CS sensitivity, and vice versa. Adjust this accordingly, and do not forget that anything you change here will likely implore you to change your in-game settings as well (depending on which, if any, noforce commands you applied).

[Mouse DPI]
Start -> Programs -> Your mouse software (if applicable).

Mouse DPI stands for Dots Per Inch. Most optical mice have a resolution of 400-800 DPI. In translation that means that the cursor on a standard optical moves 400-800 pixels across the screen for every inch the mouse is moved on the display. Mice like the mx518 can perform as high as 1,600 DPI. What this means is that the higher the DPI, the more accurate, precise, and sensitive your mouse will be. Just because your mouse is capable of higher DPI does not mean it is set that way. Just like an 8x motherboard shipped at 4x, your mouse could be set lower than it is easily capable of performing at. Consulting your user manual or company's website you can find out your current mouse limitations. By downloading the latest drivers, and then installing the proper software, you can likely raise the DPI for your mouse higher than it is boxed at.

[Mouse Frequency]
One of the most overlooked aspects of mouse performance is mouse frequency. What is mouse frequency? Well, the reported frequency is expressed in Hertz (Hz). It is the amount of data your optical mouse device sends to your system in the matter of one second. Think of it loosely as frames per second, the higher the better. There are two major factors that can drastically alter the amount of Hz you are getting. One is, of course, the mouse you have; the second is the port you use. Generally, if you are using your mouse in the USB port, you can reach in excess of 125Hz. A PS/2 port mouse can perform anywhere between 40Hz on the lower extreme, and about 97 Hz on the upper. On average most people probably get around 60Hz. Variables can show up as well, such as whether or not your mouse is wireless. There are a few utilities you can use to increase your PS/2 mouse performance. The best way would be to purchase a PS/2 to USB adapter; the other involves downloading a third party PS/2 rate adjuster. Even with a tweak utility, your USB port will still out perform, so if I had to choose I would get the adapter.

How can I test my own mouse frequency?
There are actually quite a few third party programs out there you can use. I would recommend "Andrea Binello's Mouse Frequency".

Phew! I warned you! Thankfully that is everything you need to know. Now go put all of this new-found knowledge to good use!