|1.) As Derek was mentioning, the free versions of MBAM and SAS are on-demand scanners. You can have all the anti-malware programs installed that you want, but only 1 should be real-time (aka. resident shield) enabled. I have my anti-virus (Avira free), MBAM free, and SAS free all installed.|
How did your Avira scan turn out? If you choose to use MBAM, SAS, or other scanners, please let me know about those too. I'm interested to know whether there was malware involved.
2.) I'd generally agree with Derek's definitions except for malware.The term malware is short for malicious software and encompasses all the bad stuff. It's the umbrella term.
3.) After you've checked all the areas you want cleaned, you can click the Analyze button and see how much space CCleaner will save for you. Then click the Cleaner button to delete the temp files.
It's really up to you based on your preferences. For example, if you set how often you want your web browser to delete temporary files, you don't need to clean it with CCleaner. That's why it's good to use the Analyze tool first and see what's taking up the most space. If you're not sure about something specifically, just ask.
Here are my preferences:
Windows tab: everything checked except Recent documents, Start menu shortcuts, Desktop shortcuts, Windows size/location cache, User assistant history, Wipe free space
Applications tab: everything except all options for Firefox (my web browser of choice), my 2 anti-malware programs listed under the Utilities section.
4.) The Startup tab in the System Configuration Utility lists the programs that are set to automatically start on Windows login. You can just uncheck those programs on the list, or you can open the programs and look in their options area for a startup section. I prefer configuring startup options at the program level and not System Configuration Utility. Both will accomplish the task, but my preference removes them from the startup list.
5.) If you uncheck "Use drop shadows...", the background color of your desktop icons get that dark blue color as if they're all selected. Uncheck it and see for yourself. Keeping it checked will keep the desktop icons background color transparent.
While you're navigating through your files and folders, there is a left pane with sections for Files/Folders Tasks, Other Places, and Details among others depending on what you have selected. If you uncheck "Use common tasks..." that left pane will disappear.
Once again, having only these two checked is personal preference. I like to keep my computer running well, but not at the expense of helpful features or ugly desktop icons. The rest of the visual effects waste resources, like animations, shadows, and stuff. You have to weigh in the benefits for your own preferences. For a 4-year-old computer, I think you'd be better off disabling some of the style in favor of performance.
Apologies if I don't respond to your reply immediately. I don't check this site daily, but you're welcome to PM me as a reminder.