Refer to someone else for the specs required for what your father needs.
When I buy computers, I wait for coupons from Dell Outlet. The computers are already discounted, but then you get a coupon on top of that. Currently they have a 15% off coupon, although sometimes they have 25% off coupons. Some models are scratch and dent, some are "refurbished" which means they were used less than two weeks by someone else, returned, wiped clean, and the Dell people can't find anything wrong with it. I buy all the computers for my workplace this way, including personal computers for my coworkers.
For example, I ordered an Ivy Bridge i3 laptop for my boss, 8 GB of RAM, 720p 14" screen, Windows 7 Professional. Tax included and shipping free, with a 25% off coupon applied, the order was just under $400. Then I put a 120 GB Samsung 840 EVO SSD in (now selling for $90), and it's crazy fast for that price. And I ordered an identical one for $15 more that had an Ivy Bridge i5. But since RAM is a touch more expensive now, the prices aren't quite as good as that.
Note, the Dell Outlet search and filters are absolutely horrible. Clicking on i7 processors only, for example, will eliminate 95% of the options that actually have i7 processors. And if you filter by a particular model, it will only show you a small sliver of that they actually have for sale for that model. It's just dreadful. What I do is click "compare all desktops" or "compare all laptops", ignore all filters, sort my price, and scan through the pages until I find the cheapest one that has the specs I want.
Because they are scratch and dent or refurbished (they tell you which, and the two are priced differently), there's very limited selection of what you can get. The computers go fast, so if you find one you like, put it in your cart right away, and buy it before it kicks back out of your cart.
Let me know if you want my coupon code (which expires in a few days anyway) for the 15% off.