First of all, I would say one thing above all else: SHOP AROUND. Know what you're getting, and make sure you're paying the least amount of money you possibly can for it.
Next, I would say it may be a good idea to consider a local computer shop you trust over a national chain---typically, the smaller places are going to offer lower prices to get you shop there, and as long as you don't leave your area often (or are planning on moving anytime soon), it may be a good thing to look into.
Otherwise, though, it's a good idea with a laptop to "overbuy" what you need---as the others say, laptops have next-to-nil upgradability, and finding out that something isn't good enough a year down the road will be very disappointing.
Also, if you're going to use the laptop enough, BUY THE EXTENDED WARRANTY! There are pretty much no servicable parts on a laptop, which means you can't just pull out your dead video card or processor and replace it with a new one---you've got to send it in for repairs, or often even a replacement.
Now to technical details...
Your laptop brand is a tough call... I find my liking going with either HP or Dell (in that order); you can still get a Compaq, but since Compaq is now a subsidiary of HP, it seems extraneous that HP would still offer Compaq laptops when they have their own models. Other people will likely recommend other brands, and that's cool... I will say this: I WHOLEHEARTEDLY suggest you avoid Gateway at all costs. I worked there for all of 5 weeks, and it was worse than "ridiculous" and "loathesome". Felt like NOTHING got done. If you trust them, and they have the lowest price, then go for it, but I've said my peace.
For processors, you can go either AMD or Intel... honestly, there's going to be very little difference for what you plan to be doing with it. You can go either one; I would have to say neither is going to be really better (or worse, for that matter) than the other. There are those who stand by one or the other quite religiously (I happen to strongly prefer AMD's over Intel), but it's really up to you, and the price.
Your processor speed should be at least 2 GHz if you can manage, however (overbuying here)... You won't necessarily need anywhere near that, but there are games already requiring 1 GHZ CPU's, if I'm not mistaken.
As you say, you're going to want a fairly hefty HD... I would say go at least 80 GB if you can manage, and go "7200 RPM". By RPM, that does mean Rotations Per Minute; the hard drive can spin faster, and thus has a faster access time.
You'll want at least 512 MB of RAM; With WinXP, 256 is about the minimum, but as you say, you'll have a lot of programs open, want to play games, music, etc. If you can manage, get the highest listing of "PCxxxx" memory you can find ((note that this depends on your processor bus speed; don't worry if you don't know what that means, as any major computer store won't let you buy a computer with incompatible processor speeds vs. RAM speeds))---this is called DDR memory, and is faster than the now older SDRAM. Rambus memory, if you can even find it, is likely not worth it, since the performance imporvements vs. cost ratio is way out of wack.
normal CD-ROM drives seem like a downgrade nowadays; normal "included in price" packages should likely include at least a 40x CD burner, or at least a 12x DVD-ROM (usually closer to 48x burners, or 16x DVD-ROMs)... If you want, you can even get a combo CD-RW/DVD-ROM, and I think I've even seen DVD-RW's (burn DVDs!!), but that'll likely cost you. My recommendation is the combo CD-RW/DVD drive.
Many laptops today don't actually come with built-in floppy drives... although this is personal preference, I would highly recommend getting a laptop with a floppy drive... lets you "quickly" copy (well, relatively, for a floppy drive) files to a floppy, plus lets you use boot floppies in an emergency.... and by "emergency", I mean "your CD drive isn't booting CD's" or whatnot. Either way, IMVHO, just a handy thing to have.
Most laptops have onboard LAN, plus a PS2 connector for mice or keyboards--and many have 1, 2, or even 3 USB connectors for mice, keyboards, cameras, printers, or whatever else you might want to use. Many laptops even feature an onboard wireless controller; I would say try for the 802.11g (also called 54g) wireless protocol; that's the newest (and fastest) one, last I knew, and I believe it's also backwards compatible (you can still use it with older wireless hardware). Either way, you should also have at least one, if not two, PC card slots for anything else you might want to use (including ethernet cards or wireless cards, should the laptop you choose not have those built-in).
If you can (that is, if better battery options are available), don't skimp on the battery. After all, the main point of a laptop is portability--so if you're tied to a cord cuz your battery life isn't that long, then you've sorta defeated the purpose...
That should likely be all you need to know.... If you have any other questions, have a look at one of my favorite sites,
www.pcmech.com. The forums there should be extremely informative, and the tutorials there can be very helpful.
Incidentally, I sorta wrote all this without any knowledge of just how much you know about computers... so, if this is essentially "dumb-talking" you, please forgive.
