Parthasarathy Sinha,
I don't understand that it will not allow unless there is some type of malware or permissions stopping you from changing them.
Download Malwarebytes Anti-Malware free edition, update it and do a quick scan. Remove anything it finds. If it finds anything, please post the log back here.
Download the Network adapter drivers and save them to your desktop.
| Intel Centrino Wireless-N 1000, v.13.2.0.30, A00 null | Recommended | 13.2.0.30 | 9/15/2010 | Windows 7 64-bit |  |
Make a system restore point.
Start, control panel, device manager. network, right click on Intel(R) WiFi Link 1000 BGN, left click uninstall. Tell it to remove the drivers and software.
Restart your computer. When you log back in, the new hardware wizard will try to install the adapter but fail. Install the drivers saved to your desktop.
You should be able to connect. If not, then try downloading and installing Dell QuickSet.
| Dell QuickSet, v.10.5.0.1, A00 Dell Quickset Application | Recommended | 10.5.0.1 | 4/12/2010 | Windows Vista 64-bit Windows 7 32-bit Windows 7 64-bit Windows Vista 32-bit | |
What happens?
Rick