Reader LK wants to know if Microsoft Security Essentials (which I've championed in these pages many times) can be installed alongside other anti-virus and/or anti-malware programs.
Short answer: no.
Longer answer: Definitely, definitely, definitely no.
You might think that where security software is concerned, more is better. But you'd be wrong--especially if you're talking about programs that do the same thing, like fight viruses or spyware.
For example, if you were to install MSE on a system that already had Norton Internet Security, the latter might think the former was a kind of spyware--or vice-versa. What's more, one security might not slow down your system that much, but two almost certainly will.
My advice: if you're planning to switch security tools, do exactly that. Uninstall one, reboot, and then install the other.