Network issues... and new cable modem on top of that

I finally got cable internet at the new house! I didn't realize how much 56k sucked until I had to use it for two weeks, after being on cable/DSL for the last 5 years.

Anyway, I have questions about the cable modem stuff, but let me get to the network issues that were pre-existing first... OK, I've set up home networks, and changed computers around before, and never really had any problems, until XP was thrown in the mix. Here's what I've got...

My main computer at the moment is a Compaq Presario 5280 (don't laugh, it was given to me after I lost most of my home built stuff in a fire). It runs Windows 2000. My "MP3 storage computer" is a homebuilt based on an OLD AMD 233. I think I keep it around because it was the first one I built. It runs Windows 98SE. Up until a couple days ago, these were networked with a Kingston EtheRx Pro-Series KNS800/R 10/100BASE-TX switch. When I lived in the old house (in the old town, with the old girlfriend), her Compaq Presario was also hooked up (don't remeber what model, but it was a 400MHz). It ran 98SE. She then replaced it with a homebuilt that she bought from someone- a 1GHz running XP. All of these computers operated flawlessly with the switch, and we've had both cable and DSL running with that switch (though I think I remember having to pay for additional access under the DSL).

Now, fast forward to current time... My Compaq (Win2000) and the old 233 (98SE) both still perform as they should with the switch, but the new girlfriend's HP Pavilion a430n (with XP) is giving some issues. It gives me a warning that says something to the effect that there is a problem with the network connection and it may not function properly. However, it does seem to be working as it should. It even does this when I take the switch out of the loop and run a crossover cable directly to the Compaq. I've tried different cables, had all my cables tested, etc. I just don't get it.

Problem number two- the cable guy came and hooked up the Internet. Now, I have the HP and the Compaq sitting side by side on a bench, hooked to the switch. The old 233 is under the bench, and the Pavilion 734n that I asked about in another post is sitting there too, obviously close to being done. To any normal person, it looks like I have 4 computers here networked together with an 8-port switch, so it would stand to reason that 1.- I'd like them all to be on the Internet, and/or 2.- I'd at least like them to remain networked together, since they're probably networked for a reason. Makes sense, right?

So Mr. Cable Guy unplugs the Pavilion a430n from the network, and plugs his cable modem into the ethernet port. He gets the Internet running on this computer alone. The modem he brings is a Motorola SB4200 SurfBoard. I asked him why he didn't plug it into the switch, and he said it wouldn't work that way, and that I'd have to purchase a router in order to make them all work (he recommended the Linksys EtherFast 4-Port Cable/DSL Router, BEFSR41). So, I asked why the cable modem I had in the last town worked, plugged straight into my switch, and he tried to tell me it didn't- I must have had a router somewhere! I think I'd notice that! I went on to point out that the modem he provided had a USB interface, why didn't he use that so I could at least keep the HP hooked up to my home network? He said "we don't have USB drivers for these modems, so they have to be hooked up via Ethernet."

OK, so I've never owned a router in my life, but I suppose it's supposed to get all the computers hooked to it on the Internet. Will it also get these machines back on a home network too? In other words, will it totally replace my switch?