Here's my experience: My son and daughter both have, and still use, two $299 made-for-Walmart Compaq laptops (XP). Both have survived college life with absolutely no problems; including no virus'.
I work from home and have been using a Dell laptop (running XP) since 2007. I restart Monday morning, start up about ten applications (ranging from multi-tab Explorer & Chrome, citrix windows, old DOS based legacy program, MS Office apps, MS Communicator, etc). I have a program that simulates keystrokes so it stays awake ~ 12 hours a day; all week. I only restart it once a week or when there are updates to install. No h/w, s/w, virus issues. I can ask the company for a new model, but the laptop is stable and the dual core cpu is still fast enough.
I have an Acer pc next to my work desk. I upgraded the power supply and installed a high-performance ATI video card (large kind that takes up two slots). That is going on four years old. It runs Vista with four separate accounts. My son uses it as his gaming machine in the evening and weekends. I use it mainly for photo editing, Google Earth, and e-mail. My wife uses it for the Internet, video streaming, e-mail, and Skype.No h/w, s/w, or virus issues. That pc stays powered on all the time and easily wakes from hibernation when we move the mouse. We rarely restart it.
So I cannot complain about MS OS or some of the hardware that runs it. However, I am considering getting our first Apple product (reason why I'm on Apple forums). I am concerned about the number of post about h/w and s/w issues. The number of posts seems high considering Apple PCs and laptops are only about 5% of the user base of PCs.
Just keep this in mind....
When people come online to talk about their product it is almost always because something is wrong. The average consumer doesn't seek out an Apple-themed message board to gush about the laptop they just bought that is running flawless (not saying that there aren't positive reviews out there, just that most aren't compelled to say something about their purchase unless something has gone wrong).
The same holds true for any product or service.