While adding RAM can be helpful (and running such programs as CCLeaner), it is ultimately a band-aid in the end. If you are strapped for cash, it's a quick solution that is not expensive and is easy to do.
However, if your machine came with 512mb, it is probably an ~2007 vintage machine.
Much like maintaining an old car, there comes a time where sinking more money and time into something has diminishing returns.
The mechanical parts are going to start breaking down. Hard drive's fail, heat sinks and fans go kaput and on-board devices (WiFi for example) just stop.
Linux can be great. Basic functionality (web surfing, e-mail and Office-like products) for free! When family came over for our wedding, the guest laptops worked beautifully for web surfing. Boarding passes were printed! It worked.
But even Ubuntu and Mint fails what I call the Joanne test: Can my Mom (Joanne) use it without any extensive retraining from her son 2000 miles away? :)
Would our wedding guests have been able to set up the WiFi printer and download these things call "plug ins" so they can see the latest ESPN baseball results? (Forgive me, I don't follow sports..I may be getting the details wrong. But that's what I did so a buddy could see the sports).
The average user just wants to boot up the machine, use programs they are familiar with and not have to worry about the differences between an .ODT and a .DOC file and why their iPhone, iPod and camera is not automagically syncing up????
If you are professional IT geek, or just anyone who is comfortable with tinkering, no worries about the above. Easy-peasy, mac n' cheesy.
But, again, the Joanne-test fails for above. It also fails the Mrs Mags test, too. Adrianna is typical of a user who is familiar with modern computers but has no desire to type "sudo apt-get xxxx" to get a program just to she can emulate iTunes. ;)
So, that brings up the budget question.
A low end laptop has more oomph and bells and whistles from something made 3 yrs ago or so.
Here's something for $300:
Is it the "best" laptop? Probably not. Will it do the basics and then some? Heck yeah.
That's just one quickly google search. Obviously more can be bought for better deals if someone is ambitious and wants to shop around.
>>"As the techy professional I'm often stuck fixing computers for friends, >>relatives, and neighbors"
I used to do that. Then I became smart. :) Unless it is Mom or my wife (and maybe a few select friends), I've learned to NOT do that. You fix their e-mail issue and two months later, the video card going bad is somehow related. :D At least this IT geeks wants nothing do with actually working on computers when I am off the clock.
Kinda like a mechanic: A mechanic will drive the car to get to places when off-shift, she has no desire to change your car's oil for fun. ;)