Here is a simple guide for when buying a new PC as to what you might need.
FOR THE FAMILY THAT
JUST DOES WORK NO PLAY - Be aware that your requirements will depend on the kind of work that you do and that the work load will change as you go through your career, if your work is simply emails, then consider an i3, they are a solid simple processor and capable of doing the job quite nicely. In terms of RAM and Hard Drive, a simple 3 or 4gb Machine will suffice, and for storage aim for 500Gb to 1Tb this will give you lots of storage space and room for programs such as office and whatnot.
I DO SOME PLAY AND WATCH A FEW MOVIES ONCE A WHILE - For movies, you should consider the graphics needs of the computer, as well as it's general speed. A Movie playing computer (Assuming you are playing DVDs) will need an i3 or a low end i5 processor, 4gb of RAM will be fine and storage space is quite ok if you are only playing a few simple things, 1Tb of Hard Drive is a great idea. For Games consider the idea of a Dedicated Graphics Card, they will be measured like RAM in 512Mb and up, a 512Mb is great for simple stuff a 1Gb is even better!
I EDIT MY OWN HOME MOVIES AND PLAY A BIT MORE - Consider the i5 as the heavier strain on the PC requires a more powerful processor. Also depending on the application you are going to use and the version of windows you wish to run, as to whether you are using 32 or 64 bit (By using 64 bit some programs may not work, however the PC will run more efficiently, and also allow for more than 3.25Gb of RAM to be installed at full power) Consider a good graphics card 1Gb would be a great starting point when you want to edit video. 4GB of Ram and consider a 1.5 or 2TB Hard Drive to give your PC a good buffer. Also consider stepping up to a Blu-Ray Burner at this point, they are not much dearer than DVD Burners and give you extra versatility for later on as well.
GAMING AND HIGHER END - For higher end functions, step up to an i7, they have grunt and speed where it counts, you will already be using 64 bit and thus can use 8-16GB of RAM, also you will use Solid State Drives instead of Traditional Hard Drives, consider using an SSD for your Operating System with a Traditional Hard Drive to lower costs. When looking at your Graphics, consider using a twin card system, it will require two PCI-e ports on your board, but will give you a lower operating temperature and allow for better performance.
In terms of costs, you should consider what you can afford, A budget PC can cost as little as $400-500, however it may not suit your needs, so to make things easier here is a simple bracket. These prices are for Towers only!
Budget (Email etc.) - $600
Movie Watching - $800
Movie Editing - $1300
Gaming etc - $2000
These are rough retail prices and depend on your ability to strike a deal :)
Take care, hope this revision is much more helpful than the old version!