I can only give you this recommendation but rest assured we uses this in our college network administrative level PC and all over the network.
I my friends all so do this.
First you can't use Two Virus gurads on your PC .
Why ? Windows protocols commands will go hay wire
Why again ? If you do install let say as an example Symantec & Bit defender ....
The first installed virus application will not be able to function it's windows operations while at the same time secondly installed virus application all so will not be able to function it's operations as well.
They will be competing with each other to gain access to Windows kernel operations rather than to protecting the PC.
This is not FUNNY ! Understand that very thoroughly at all costs.
In another words each virus guard will stay away from Anti virus operations Assuming that other Available application must be the Anti virus program and VISE - VERSA.
So how do you do it?
Install a your choice of Anti virus program and all so Install a Anti spy-where program after viewing what's best for you (your choice again)
Now you might ask WHY ANTI-SPYWHERE ONLY? ? ? ? ? ?
Currently EXISTING anti virus applications do allow an Integration of SECONDARY HOST to there anti virus program. Even though anti virus programs do have it's OWN ANTI-SPYWHERE component to it self . It allow Integration ONLY ANOTHER ANTI-SPYWHERE application where it will (it has to) be SUPERIOR (Virus guard) and the anti-spywhere is INFERIOR. (Master - slave)
This the only way you can achieve what you have asked .....
So what are good ANTI SPYWHERE programs ?
Sunbelt Counterspy
Web root spy sweeper.
These are the only very best available right now.
We have installed Symantec NIS 2009 and Counterspy in our College for more than 18 months.
And my PC have Symantec NIS 2010 and Counter spy all so. And I been using counter spy Integration ever since 2008.
If you really do want Dual layer protection this the only PERMITTED , ALLOWED way and manner it can be achieved.