(ALWAYS RUN AND SAVE SYSTEM RESTORE POINTS BEFORE AND AFTER INSTALLING OR UN-INSTALLING ANY CRITICAL COMPONENTS OR SOFTWARE!!)
Besides the fact that running multiple firewall or spyware guard and removal programs together will conflict with each other; different defense programs have, or search for signatures related to attacks. Something listed by one of these programs can easily show up as an attack or initiate a defense or (Access violation) and cause itself or another program to stop working properly or not at all.
Example, older versions of Spy-bot would list "file sets", or versions of attacks in a file that Spy-bot protected against, While older versions of Norton for example would see these and warn or initiate a removal of that reference. The actual file or program was nothing more than a reference in your registries and or settings of Spy-bot (advanced mode).
Comcast customers who use Norton 360 (Comcast version) should note that: Windows firewall, Windows Live Essentials, and other firewall or spyware removal programs can cause the same dilemma if run together or at the same time. One of the reasons why you are asked to disable or close these programs while installing any other number of programs is to prevent some of these same occurrences.
My suggestion to you before deciding one program or another is useless or better than another is to decide which ones you want to use. You need firewall and virus intrusion or protection software. Some combinations of these will or won't work together. In my experience, Norton and Spy-bot work well together under most circumstance if they are the only Two you use. Although, installing Spy-bot first before Norton allows Norton to recognize newer versions of Spy-bot as a form of virus protection and from there their default settings works well. Installing Norton first does not always work the same. Norton 360 all by itself without spy-bot, Live essentials or Windows software has all the features you need if you know where to look, (Registry Cleaner, Program removal or disabling, backup services and more). Spy-Bot does not have a couple of these features so I include "CCleaner" from Piraform, not File-Hippo. File-Hippo wants you to wait and offers other software you may not want.
So for me, your programs may differ but the result is the same, I would first download and save the install program and not install right away the programs I want to use. I would then, disconnect from the internet or network you are on to avoid intrusions or attacks. If you have these or multiple similar programs installed or running, I would then completely shut them down or disable these programs and background processes so that uninstall will be unhampered and more complete.
["CCleaner" is a good program for closing any and all running processes via it's "Tools" section and then "Start-up". Programs can be disabled or removed as well from the "Uninstall" tab in tools. This is also a great program for cleaning your registry entries, temp files, and various settings of software saves. BE SURE TO BACKUP AND SAVE BEFORE AND AFTER CHANGES JUST IN CASE ]
I generally install in this order for my choices, CCleaner, Spy-Bot, Then my Norton products. I disable or don't use at this point, Windows firewall, or the security section of "Live Essentials" unless these are my choices, then I would only use CCleaner, Spy-Bot, and then install or re-install the other software I choose in that order. Spy-Bot needs to have updates first, then a full scan of your PC, then immunization ran to protect your remaining software in your system before continuing installs of your chosen Programs. Both CCleaner and Spy-Bot for Windows 7 especially need their .EXE file properties set to run as Administrator first in order to work completely and properly.
All other settings in advanced modes for these programs are generally safe and should not be changed without specific knowledge of how to use them.
In conclusion, Clean, Fresh installs usually solve these issues when done correctly. Continue to install your Firewall/virus-guard software and then reconnect to your network or internet to get further updates. Finally, run any last scans to get a good starting reference point.