Q:

netsh wlan command not found in windows xp

am not able to find netsh wlan command to connect to wireless networks. 
How do I install this service on windows xp ?

A:

You can't find it because the netsh wlan command exists only in Windows Vista, Windows 7 and in Windows Server 2008.
The netsh from Vista will not work on XP.
From Technet Article from Microsoft explaining netsh wlan:

Applies To: Windows Server 2008,Windows Server 2008 R2
...
The commands documented in the Netsh WLAN reference for Windows Server® 2008 can be run - as documented – on computers running Windows Vista®.
Likewise, the commands documented in the Netsh WLAN reference for Windows Server® 2008 R2 Release Candidate (RC) can be run - as documented – on computers running Windows® 7 RC.

