Big question, bigger answer.
First of all, when it comes to nicely priced computer systems and first time buyers I would recomend a desktop instead of a laptop. A laptop gives you the convenience of being able to move your system around and that's about it. And for that added convenience you're going to shell out a lot of extra money and be befuddled by an array of plug and play devices. What I mean is that laptops only have room for a CD/DVD drive and a Hard drive and that's about it; everything else (3.5" floppies, networking cards, modems) are all plugged into ports on the computer. No big deal really, but if you want to use those things it's quite a hassle to string up all those cords and carry around all the extra gear. Still, if you're looking for that portable convenience a laptop is fine, but if you're just going to keep that system in one spot go desktop (you'll save tons of money).
Now, as far as processor speed goes you can get a lower end Intel Pentium system or AMD Athlon system (1-1.4 Ghz) for a good price. A processor like either of those is more than enough to handle office programs, games, and 2D graphic apps. Now if you want to run 3d graphic apps (e.g. 3D Studio Max, Maya, Art-lantis) you will need a high speed processor (1.8 Ghz or above) with lots of Cache memory. However, from your opening post I don't think you're in the business of using 3d design apps, so I'd say just stick to processors in the 1-1.4 Ghz range (higher if you want, but it'll just be overkill if you're only going to run Excel).
When it comes to gaming the processor will be fine, but the killer for gamers is the video card. Sh!tty video card = horrible gaming. And, when it comes to video card, NVIDIA is the best. You can put a very decent video card into a computer for about $150 (like the GeForce 4 MX series). A cheaper option would be a GeForce 2 which you can get for about $80; and a more expensive option would be the GeForce 4 Ti series which could run you upwards of $400. I've got a GeForce 4 MX and despite the stereotypes around this card, it's a very good, solid card and works very well with my slightly slower 733 Mhz system. Also, when it comes to video cards,
DEMAND AGP. The other option are PCI (bad) or integrated (absolute rot). AGP is an interface for graphics cards designed specifically for graphics cards (as is said in the name; Accelerated Graphics Port)
As far as RAM goes, there is no such thing as too much. I'd say 256 MB is plenty for what you want to do with your computer. But when it comes to gaming RAM equals kicking ass. 512 MB makes for a great gaming system. That part isn't so confusing as the next part. There are different types of RAM. The first is SDRAM. This is nicely priced (you can get 128 MB for $20) but is a little slower than it's counterparts. DDR and RDRAM are far more expensive -almost twice the cost- but significantly faster. However, you'll only notice this difference in speed between these types of RAM if your going to run some serious sh!t like 3D Studio Max.
Other things to consider:
As far as hard drive space is concerned, you'll probably never use more than 20 Gigabytes worth of space for what you want to do. Hell, I survived on a 10 GB hard drive for a year and half and never used all the space. That was untill, of course, I got Broadband and started downloading mass software (now I've got an 80 GB hard drive that's full of all sorts of that junk).
For internet access, you should consider what you'll be doing on the net. In all honesty, DSL or cable internet is only necessary if you're going to be downloading constantly like me. If all you're doing is the occasional posting here or trifling research a dialup connection will do you fine. For that all you'll need is a modem, and when it comes to modems the fastest and just about only model you can get is a 56K v.90 modem. These are really cheap and even if you're not going to go dial up, you might as well get one for a rainy day when the DSL line is busted all to sh!t.
If you're looking to get Broadband, get an ethernet card. It'll come in handy if you want to network computers too, but I use my ethernet card solely for internet connectivity. See, Broadband modems will either connect to your computer via an ethernet connection or serial port. I like to use the ethernet card, some people prefer the serial ports. In any case, an ethernet card won't run you more than $10.
A CD-RW drive is another consideration. You can get a good one for $150 bucks (the best name is Plextor). I live by my CD-RW. I've burned hundreds of CDs with it. Music CDs, VCDs, Divx, ISOs, and system backups have all found their way to my CD-R collection.
All told, you can get yourself a minimal system for under $1000. I'd recomend you spend between $1200 and $1600 on a system. That way you won't be wasting money on a top-o-the-line, but will still have a nice system that will last you for years. I bought this one for $1600 at least two years ago and it still kicks ass (I have upgraded it, though).
Oh, security issues. Get an antivirus program like Norton AntiVirus or McAfee Antivirus to protect you from those punk ass strains. To protect yourself from script kiddies, spyware, trojans and the like get a firewall. You can pay for one like Norton Personal Firewall, but you can get a free one on the net like ZoneAlarm, BlackIce Defender, or Tiny Personal Firewall. Most of these also have pay versions.
). I dont want the BEST money can buy, just be "adequate" - I'm on a fairly tight budget.
. And keep your level of detail... that is, don't condense the juicy stuff out 
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