[DonRotolo]

All reasonable choices. You might consider 800 MHz memory if the price is reasonable (maybe a 10% premium?). Also a larger SATA drive (although that's quite a good drive), 250 GB or 500 GB are actually reasonably priced, BUT you can always add one later for data.

Add-ons: Get a large-as-you-can-afford USB (or firewire) external Hard Drive, and good backup & restore software like Norton Ghost. Very handy of something goes horribly wrong, you can just bring your machine back to where it was (even if you need a new HDD) with almost trivial simplicity. Get good anti-virus & general firewall software (above & beyond XP's) and pay for the update subscription.

You only need a modem if you intend to use a telephone line to communicate with another computer (or the Internet) - a Cable or DSL modem is an external device usually provided by the Cable or DSL folks.

The case might be overkill, but again I'm conservative - if you like it and can afford it, get it. (My personal preference is plain vanilla cases with 350-400W Power Supply - but cheapo cases are LOUD). Don't underestimate the fan noise!

The hardest part will be loading XP onto the HDD - but that's how you learn. It seems like every new machine I built, every serious problem I had to fix, all took 3 days, but I did learn a LOT in that time. Don't sweat it, it's not that difficult, just follow the instructions and ask for help if you need it.

Good luck,
Don