I would not recommend purchasing a computer if it will be a mission-critical machine where it can't break down. If all you do is word processing and email, then go ahead and buy yourself a computer. But keep in mind that I've (and many others familiar with computers) have seen no-name hard drives, underpowered power supplies, motherboards just micromillimeters from the metal frame, monitors that die in 6 months ude to a cheap inverter or backlight, and on and on and on. I was on a two-month convention and I needed my own laptop so I wouldn't have to use hotel computers at their business center and I regretted my purchase. And then I bought a Compaq about a year and a half ago, and I opened it up to do the routine dust removal I always do, and the power supply is 250 watts! And this was an Athlon 64 with 1 GB RAM, the whole enchilada! The $300 or so cost really showed.
I recommend that you save yourself from doom down the road and build. If you buy, you will be tempted to spend more money and, in my case, upgrade the mediocre 250 watt PS to about 350 and replace the hard drive with a Seagate as that Compaq had a Samsung. God only knows what was in that Dell laptop.