Don't put in the offending Ethernet adapter/card etc, and load up several anti-malware programs and run them.
First try malwarebytes
http://www.malwarebytes.org/
AVG Free
http://free.grisoft.com
Superantispyware
http://www.superantispyware.com/download.html
Spybot Search and Destroy
http://www.safer-networking.org/en/download/
Adaware Free
http://www.lavasoft.com/products/ad_aware_free.php
You should eliminate a malware issue being the cause first.