For a medical doctor, your grammar sort of sucks :)
Get a Toshiba. If you want a PC, the most reliable computer will be a Toshiba, every laptop we've had has lasted for years (the oldest one is getting to be over 10 years old soon). People will tell you to get a Dell - Dells are reliable *if you pay for it*. If your laptop is under $1000, you're throwing money away, so don't look at the Dell options that try to sell you a 3GHz, 3GB computer for under $1000. HPs used to be reliable, but I don't trust them anymore. Don't even think of buying an Acer, they're guaranteed to break down. So Toshiba Satellite series is a good choice, though they are slightly more expensive, but the investment is well worth it.
New computers now come with Windows Vista. People complain about it, but it's a great system to use once you get used to it, and if you haven't been using computers a lot, you won't have trouble getting used to it (I'm a classic Windows person, I don't even like the XP layout, but I'm super conservative).
I suggest a laptop, but if you want a desktop, then you have a lot more choice. They are cheaper, have more capabilities, and Dell desktops are pretty good, HPs are also good. I am currently using a Samsung flat screen monitor, and enjoying it. However, Acer is still a bad, bad, bad choice. For a desktop, you can get 4Ghz, 4Gb RAM, with about 80GB space for $600 if it's custom built Dell, plus your monitor will cost you maybe $200 for flat LCD.
If you're not looking for anything fancy, just net surfing and DVD burning and printing, you can talk to someone at Future Shop or such, they can definitely help you. They become useless when you're looking for something more specific, but for a simple workstation, Future Shop/other tech stores tend to be pretty helpful.
For people recommending MacBook air: you can't burn DVDs on it. It doesn't even have a CD/DVD drive. AFAIK.