>>>Unfortunately that IP address would already have a DNS entry at the ISP, so I wouldn't be able to use it for my purposes (like running an email server or FTP server). Looks like I will have to pay the piper.
>
>>You can run FTP/eMail and Web servers from a single IP address. They each use different default TCP/IP ports. You can even run multiple web sites by making use of Host Header processing.
>
>Can you point me to some info on doing this? I am also assuming that my DNS server will need to have its own IP address. So the minimum I can get away with is two IP addresses right?

I think you'll be able to get away with just one IP address. You can run a DNS server along with email, ftp & web, all on the same PC hardware, accessible at the one IP address.

When you install the server software (on whichever o/s you choose) the individual services should all set themselves up on the correct default TCP/IP ports (Web server = port 80, ftp server = port 21, eMail = 25/110, dns = 53, etc.) Under Windows, the file \systemroot\Winnt\System32\Drivers\Etc\Services lists all the default port assignments.

DNS might be a little awkward though. How would you get your domains registered? You need to provide references to two DNS Servers when registering a domain, and I'm pretty sure that you can't run two DNS services on 1 IP address.

I have a server co-located with a hosting company. I do run DNS on the server, but my registrations are carried out by my hosting company and they name their DNS Servers for the registrations. I make all DNS changes on my server, which then broadcasts the changes to the DNS servers belonging to the hosting company.
(Buy the excellent O'Reilly book on DNS under Windows NT).

I got some info from this forum before on Host Headers (for multiple web sites on 1 IP), so try a search in the KB. (My membership is lapsed just now so I can't provide references for you)
If you can't find the info, let me know and I'll eMail you something.