"Hardware Radio Switch is off". Where do I find this on my Inspiron laptop?

The switch is on the F2 key.  This is explained in the PC manual.

Do you have McAfee? McAfee was updated at about the same time as the last batch of Windows 7 Updates and it seems to be the cause of internet conenction problems for most, if not all, McAfee users.

See this "critical" McAfee notice -

Some customers may experience a loss of network connectivity and/or errors in McAfee Security Center after a recent update

You should do the McAfee fix, if applicable. There are corresponding notices for their corporate products.

I've had to run the McAfee MCPR removal tool a few times before and it caused a licence problem if the PC was not connected to the internet during the removal. The McAfee support chat had to reset their records to allow reinstallation-reactivation. Here's their chat link - McAfee support - contains the link to chat

I had McAfee but the connection started working again of its own accord so I thought I was clear of problems. However, when I checked it said it had been doing routine checks for updates but failed when I told it to do one manually. So staying with McAfee without following their fix procedure would have put my PC at risk by not being updated and, as further McAfee announcements have since explained, the application was not referring to its threats database correctly [and this might account for some of the variability in fault symptoms but all involved some loss of internet connection]. Actually, I removed McAfee then installedMicrosoft Security Essentials instead & my IE response is quicker than I have known it [even though I had had the McAfee add-ons disabled for ages].

This will be documented in your user's guide which should be on your hard drive.  Look for it by going to Start -> All Programs -> Dell.  It's different on every make and model, so you'll need to check with that user's guide or call Dell and give them your service tag.

 Good luck.