Ok a few choices here.
This has a decent CPU, 4GB of RAM, 1TB hard drive, a DVD burner and a seperate graphics card. Nothing game worthy but it's more powerful than just having integrated graphics. Do you like the case though?
http://www.newegg.com/Product/Product.aspx?Item=N82E16883229296
This one is more traditional. Better CPU, better RAM and a bigger hard drive but it has integrated graphics. Plenty for internet and watching DVDs.
http://www.newegg.com/Product/Product.aspx?Item=N82E16883113183
A little more money but still under your $800 limit. The most powerful CPU of the bunch and more memory ( 8GB ) Still not a gaming worthy graphics card but a good one for HD video. The most futureproof of the bunch.
http://www.newegg.com/Product/Product.aspx?Item=N82E16883229284
Just some ideas from looking at newegg. For their prices they are all good deal. Let me know if you want more options and what you like/dislike about what I picked. All have 1 year warrantys.