I suggest one fo two routes...
1-
http://www.dell.com I love Dell computers. They are well made and last along time. Takes but a few minutes to find what you need and they got decent enough customization options and you can get ongoing warranty and support/tech help options for someone who isn't a techie when it comes to computers. They have a number of different levels of computers you can get and have some nice packages. The support you can get is the big plus ehre though.
2-
http://www.pricewatch.com A whole slew of brands and independant places that will build you a computer. Generally will be a bit cheaper than Dell but doesn't have the ongoing tech support options as a result. More computer bang for your buck but you're generally
far more on your own if things go wrong.