Looking for help building a midrange gaming PC

What will you be doing with this PC? Be as specific as possible, and include specific games or programs you will be using.

I want to be able to heavily mod skyrim, keep up with some of the newer games, and run the most demanding ones on medium graphics. I also want to be able to hook up a 2nd monitor to use regularly

What is your maximum budget before rebates/shipping/taxes?

around 850 would be great, I can go over a little

When do you plan on building/buying the PC? Note: beyond a week or two from today means any build you receive will be out of date when you want to buy.

within the month

What, exactly, do you need included in the budget? (Tower/OS/monitor/keyboard/mouse/etc)

tower, OS, 1 monitor

**Which country (and state/province) will you be purchasing the parts in?

Pennsylvania, US

If reusing any parts (including monitor(s)/keyboard/mouse/etc), what parts will you be reusing? Brands and models are appreciated.

planning on buying cheap mouse/keyboard that don't need to be factored into budget

Will you be overclocking? If yes, are you interested in overclocking right away, or down the line? CPU and/or GPU?

no

Are there any specific features or items you want/need in the build? (ex: SSD, large amount of storage or a RAID setup, CUDA or OpenCL support, etc)

no

Do you have any specific case preferences (Size like ITX/microATX/mid-tower/full-tower, styles, colors, window or not, LED lighting, etc), or a particular color theme preference for the components?

no

Do you need a copy of Windows included in the budget? If you do need one included, do you have a preference?

yes, preferably windows 7

Extra info or particulars: n/a