Hey; semi-pro recording engineer checking in.
First of all - the only advantage of using a laptop for recording (over a desktop) is portability. If you just want to have a PC for recording, you’ll save upwards of $1,000 by using a desktop rather than a laptop.
Moving on -
First off, you definitely want to replace that hard drive; at 4200 rpm, it’s going to choke when you try to do multitrack audio. Like Yoyodyne said, you want a 7200rpm hard drive, bare minimum. The standard for audio PC’s is to keep a second hard drive for audio only; think of it as a spool of tape. I don’t know if laptops even have space for a second Hard drive, so if you only have one, you definitely want it to be as fast as possible - I’d even spring for a 10,000rpm one if possible.
Also, you’ll want to upgrade the RAM; when it comes to audio work, there’s no such thing as too much. You’ll want at least 1gb of ram, but I’d spring for more because 1) your video card uses “shared video memory,” which means that it uses up to 64mb of your system ram and 2) if you have enough ram, you can turn off virtual memory, which is your PC using your hard drive as temporary RAM. If you’re already using some of your RAM for video card functions and using RAM-hungry audio programs, your PC will want to hit that hard drive for more “virtual ram.” Since you’re already going to be using your HDD for both programs AND audio, you don’t want a third thing trying to access it.
Luckily, you have a Firewire port on the laptop. You definitely want to go with Firewire over USB when using an audio interface, because (to avoid a bunch of boring, obtuse technical lingo), “it’s better, and you should always choose it over USB if possible.”
This is where it gets tricky - what do you need out of an audio interface? Audio interfaces are an entire category of equipment, so it’s really up to you to choose one according to your needs. Are you planning on laying down one track at a time, and overdubbing? You’ll only need something like this. But if you’re planning on recording a full drum kit or ensemble at once, with 8 mics each going to their own discrete channel, you’ll need something like this. Most likely, you’ll want something in the middle ground like this, with a mix of 1/4" instrument inputs and XLR microphone inputs, as well as digital IO. In fact, you could even use your Fostex VF80 as a sort of submixer, sending the output over SPDIF into the PC.
On the software side of things, it depends what you need. Do you just want a software “tape machine,” or are you intending to also use virtual instruments, synthesizer plugins, samples, loops, etc? If you just want a “software tape deck,” check out Adobe Audition (formerly known as CoolEdit Pro) or Steinberg’s Nuendo, either of which will let you multitrack, mix and edit, plus apply effects. If you also want to incorporate midi sequences alongside your audio, as well as software synthesizers, loops, and samples, check out either Steinberg’s Cubase (SL or SX, depending on your needs) or Cakewalk’s Sonar. Of the two, Cubase is considered the more “professional” program, and the price reflects it. Either of these companies offer free demos, and depending on the audio interface you purchase, you’ll probably even get bundled "lite’ editions of some of these.