If you have your Cable Modem hooked in through USB be sure to have drivers for that so you can still use it. As well as if you have it through your Ethernet Card, drivers for that. I'm not totally sure what Road Runner does, but I'm fairly sure that it will give you Dynamic IPs, where they only change if your modem is reset, or turned off. In that case you really don't have to do much to get the internet going, in some cases it might already work. Static IPs you would have to input yourself, although I highly doubt thats what they've given you.
Decide which OS you want to use, of course there are many. I'd suggest if you want to try out new ones partition your hard drive, although you only have 6gb.
If you don't feel like going all the way to XP try out 2000 first. Both are much more stable than 98. Although neither have pure DOS, so if you still want DOS you'd have to go with 98 or partition a small section for DOS stuff, including DOS.
After you choose which OS you want make sure you have a CD for it, who cares if its pirated or legal. Make sure you back up everything you want onto floppies, cds, or other media. Get a blank floppy, or one that you can use that has nothing of importance on it. Insert and go to start/settings/control panel/add/remove programs. I believe under the Windows Setup tab there is a button which can make a boot disk for you. Click it and then go through several things and then after its done reboot and boot to the floppy. Finally make sure you have everything you need for the next step will erase it all. Type at the command prompt format C:
Wait while it obliterates your hard drive and then after you're done insert which ever OS you decided to go with. If you chose Windows 2000 or XP, remove the floppy and stick the CD in. Reboot your computer and boot to the CD. If that doesn't work then boot again to the floppy with CD Drivers and go to the CD ROM drive by typing D: or E: depending on what it defaults it to. Type cd\winnt
winnt
It should go through and start up the installation.
Now if you wanted to go through 98 you should instead of rebooting to the CD you can just boot up with CD ROM drivers and change your drive to the CD ROM and type setup. It should go through some tests and then install.
If you bought an OEM computer such as a DELL, Compaq, or whatever then instead of providing you with an OS CD they provided you with Restore Disc. Instead of formatting and all that junk you could just boot to the Restore Disc and then it should format and restore everything to the original factory condition.
After that you're ready to go. If you do decide to go for 2000/XP and still want DOS, for partitioning I recommend Partition Magic. Excellent software, just resize your hard drive to whatever you want for the OS and then leave whatever amount you want for DOS.