Well you have a good start. Since you want a laptop, it will be a bit easier on you to buy, as you won't have to pick every single part individually by brand/capabilities/etc. as you would if you were custom building a desktop.
So what I would suggest first is going to some of the big name manufacturer's websites and looking at their 17" models with num pads. If the num pad is a required feature you MAY find yourself limited to HP notebooks as I don't recall seeing a Dell machine with one included. But anyway, do reconnaissance work on Dell, HP, maybe Lenovo. Then go to your big box electronics store of choice and look up what you can get for $700-800 with your specs there. Most likely the specs are going to be similar, but there will probably be a bit of variation from machine to machine and if you buy one online, depending on the price you might be able to afford to upgrade parts that are important to you.
Now just going over the parts you listed. You want a good idea of what each of these does and what you think is more important than other things when picking and choosing between the different machines:
Processor - How much power your computer has. Currently most computers are running the Intel line of i3, i5, and i7. That is in order from least to most powerful. I do extensive gaming and engineering work on my laptop (A Dell XPS system) and an i5 is more than enough for me. The i7 is known to run very very hot, which can be a problem for laptops. You won't be able to use it in your lap easily and you'd need to buy an external fan to keep your laptop cool. I'm not sure how much high powered stuff you plan on using, but for internet/small business i3 would probably be fine, maybe an i5 if you find a good deal or want to be on the safe side.
Operating System - Windows 7 is fine and 8 isn't out yet anyway. It's not the resource hog that Vista was, though I am sentimental and prefer XP a little. The only advice I have here concerns if you want to use your old software on a new machine. Windows 7 is 64 bit, which basically means it works completely different from the old 32 bit (Windows XP, Windows 98, etc.) systems. If you have old software that you want to still be able to use, though nothing is guaranteed (Google "program name" windows 7 to see how other people are faring with it) then you should splurge for an upgrade to Windows 7 Professional, as it has an XP mode to handle the things the Home edition can't. Usually an operating system upgrade is an option when making your laptop online. If you're buying off the shelf make sure you know what system is coming with it, and inquire if you can upgrade if you find an in-store you're in love with.
Memory - RAM is a measure of how much "stuff" your computer can do at the same time. As a gamer/engineer I usually buy as much as humanly possible. If you don't think you'll be doing too much at a time you can go with a lower number. 4 GB might be good. 2 GB is kind of on the low end right now. Someone who is a more casual user could maybe give more input on this topic.
Hard Drive - Storage is cheap. Most laptops will come with at least 250 GB and I've never even filled up that much. Unless you're planning on illegally downloading all of Hollywood space will likely not be an issue. Just make sure it has a few hundred and don't worry. You can always make backups. BTW you'll see some laptops with "solid state" harddrives. These are smaller harddrives which are supposed to not break as easily. Don't worry about those, the technology is new and in my opinion not worth the premium paid just yet. Just back up your stuff periodically.
Optical Drive - If you are going to be burning a lot of stuff to CD (I'm guessing due to business, etc.) or playing/ripping a lot of music or doing anything with a CD, make sure your laptop has an optical drive built in. A lot of machines are trying to be ultraportable nowadays and manufacturers are leaving out internal optical drives. Which means you have to buy an external and hook it up via USB if you need to use a CD. Which can be really irritating.
Graphics - If you want to do any gaming or graphic work or movie editing at all, make sure the system has what is called "discrete graphics." "Integrated graphics" means the computer renders graphics off of the processor. "Discrete graphics" means it has a separate little chip that works solely for graphics, so you can get better results and more power. If you aren't gaming and just want movie editing or something, I would just suggest any system with discrete graphics. If you want to game, pick up a box in the store and get an idea of a game's recommended system requirements to see about how many GB (I think 2 at the moment but it's been a while since I've bought a machine) people are designing for nowadays.
I hope all that helped and I didn't overwhelm you! If you have any questions just ask. Good luck!
