A short url for accessing this page is at http://nixgeek.com/fixwin/

Enable / Disable the Hidden Administrator account on Windows 7 or Vista

Microsoft Fix It Solution Center - It doesn't get much easier than this: Select a device or program, select a problem area, then browse the tips and programs that Microsoft offers as a solution.

PCWorld - Articles seem to be kind of dated but still some good information in here

Microsoft at Home - Fix common PC problems - This guide from Microsoft covers the basics for keeping a healthy PC, plus tacks on some tips for locating problems. Reading through this should let you know if you have a software, hardware or connectivity issue and give you the smarts and apps to tackle it.

ESET Online Scanner - Free online Virus Scanner from ESET

Kaspersky Online Scanner - Free online Virus Scanner from Kaspersky (has been offline recently, good option if it is working again)

TrendMicro Housecall - Free online Virus Scanner from TrendMicro

Malwarebytes Anti-Malware (Download) - Very good malware scanner and removable tool. The official website is good, however they usually forward you to CNET's Download.com which has started to do some very spyware-like practices themselves so I recommend downloading from FileHippo instead

SuperAntiSpyware (Download) - Another very good anti-malware scanner and removal tool

A short url for accessing this page is at http://nixgeek.com/fixlinux/

TuxRadar's Guide - An older (2009) list but still some good info

YeoWorks Ubuntu Solutions - One Click Fix for common Ubuntu problems

A short url for accessing this page is at http://nixgeek.com/fixmac/

Apple Discussions Support Forum - You can select the topic by OS, program, hardware or just type your problem into the search box.

CNET's MacFixIt Feed - Tech blog CNET keeps tabs on all their OS X-related updates with the MacFixIt blog. Head here to search for updates, cool features and troubleshooting.

Quora - Apple Products - I've linked directly to the Apple-Products section, but really just punch in whatever you are having a problem with and search. Answers are provided by other users of the service, I don't tend to use this all that much but others swear by it.

The MacRX Category on Cult of Mac - Cult of Mac keeps it simple: All Mac, all the time. Follow their troubleshooting-specific MacRX category to get updates on everything from good Mac maintenance and un-deleting files to how to fix start-up problems and get your Mac running fast.

Macworld Forums - Typical forum site with categories, search, etc.

macnn - Typical forum site with categories, search, etc.