XPS 420 - Wireless Adapter Continuously Drops Internet Connection

I have an XPS 420 PC running Win Vista SP1 32-bit which was purchased in 2009.  It has all Window Updates installed.  My Internet connection is through a Verizon DSL Actiontek router model # GT784WNV using a wireless connection.  This router replaced a Westell router in late summer 2014.  This PC had no problem keeping a connection to the Westell, but the wireless connection with the Actiontek drops out regularly and only provides limited connectivity.  Eventually after 30 minutes to an hour the connection picks up again.  

There is a Dell Wireless 1370/1470/1390/1490/1505/1395 WLAN Driver listed on the Dell Drivers page which has update date of March 2014.  I have not attempted this driver update yet.

All other computers (laptop running Win 7 and two tablets running Win 8.1) have no problems with the WiFi connection.

How do I troubleshoot this problem?