Solving common Windows problems

Help Clueless Relatives with Their Computer Problems - Lifehacker
Despite the uncharitable title, this looks like a good start for resolving serious problems with Windows computers.  The article has suggestions to deal with common problems, such as:

• "It takes forever to start up."
• "I keep getting a pop-up saying I need to pay for my antivirus software."
• "When I get on the internet things look weird" or "I keep getting these annoying popup ads."
• "I can't find the digital photos I downloaded last month."
• "I'm running out of hard drive space." 
• "The internet stopped working."