If I were you, and this is only my opinion, I would disable Windows Defender. In my experience using it, it has never found any malware or informed me of finding any malware, whether running a random scan or operating in "real time"...It's a waste of hardware resources
So now we're down to Spybot, Spyware Blaster, and Malware bytes..
Malwarebytes is an excellent "on demand" virus scanner. It doesn't run in "real time" so you don't have to worry about it conflicting with any other anti malware programs.
Spybot is also a good "on demand" scanner, but I don't recommend using the "tea timer", because it keeps a check on every little thing that happens in your registry and is quite annoying.. . (Disable the tea timer)
I've never used Spyware Blaster so I can't tell you how good or not it is..
In short my recommendation is to keep Malwarebytes on there to run random virus scans at your convenience (weekly is good, just be sure to update it before scans), Keep Spybot (but disable the tea timer), disable Windows Defender... As for Spyware Blaster, I suppose using it wouldn't hurt, but you don't want too many programs cluttering your HDD, so I'd dump Spyware Blaster...