For $300, you should have access to some reasonably priced refurb Lenovo T series, HP probook/elitebook series or Toshiba portege/satellite which should meet your needs and should last 3-4 years easy. You can never guarantee hard drives and ram though regardless of brand and price. Luckily, those are easy to swap and replace.
Staples has some really crappy refurbs at times though. Don't feel bad in returning those within the 30 day window if it's really crappy.
http://www.calgary.ca/CA/fs/Pages/Su...-Auctions.aspx
I checked out calgarygringo's suggestion for the surplus laptops, and those are good ones to consider too. Beyond price, they're good business grade workhorse laptops. Pretty much the equivalent of a refurb at staples I presume. You might need to dish out a little extra to upgrade from Windows Vista though.