The path is now managed by Windows 2000 / Windows XP and not the autoexec.bat or autoexec.nt files. To change the system environment variables, follow the below steps.
1. From the desktop, right-click My Computer and click Properties and then
if Vista go to the Advanced system settings on the left of the window
2.In the System Properties window, click on the Advanced tab.
3.In the Advanced section, click the Environment Variables button.
4.Finally, in the Environment Variables window (as shown below), highlight the Path variable in the Systems Variable section and click the Edit button. Add or modify the path lines with the paths you wish the computer to access.
Akshay Adiga's Blog 