Users with the DWL-G630 and other wireless LAN cards have experienced a blue-screen error message, "DRIVER_IRQL_NOT_LESS_OR_EQUAL" with a mention of the file ar5211.sys.

This answer is specific to the AR5211.SYS file. If you are getting this error message involving a driver other than AR5211.SYS, please check other Microsoft search results for the DRIVER_IRQL_NOT_LESS_OR_EQUAL message. The following suggestion does not apply to you.

The following steps may solve this problem in versions of Windows XP:

In preparation for these steps:
A. Download the latest version of the DWL-G630 drivers from support.dlink.com.
B. Consider setting a Restore Point. For additional information about System Restore, click Start, click Help and Support, type system restore in the Search box, and then press ENTER.

1. Go to Add/Remove Software
2. Remove your G630 software
3. In Explorer, go to %windir%\system32\drivers and, if you see AR5211.sys, rename it to AR5211.old. (Note: it may have already been deleted by Step 2, above.).
4. Reboot your computer and log on
5. If Add/Remove Hardware wizard comes back up, choose Cancel
6. Install the latest DWL-G630 software that you downloaded earlier.
7. The software should install and your network card should now be enabled or detected. If it is, proceed normally. If it is not...
8. ...Click Start, Run, and run compmgmt.msc and open Device Manager ... click the name of your computer at the top of the tree, then click the icon to scan for new hardware

This was discussed here.