i can see this will turn into a quagmire of "yes it is", "no it isn't" posts if we're not careful.
linux does have a lot more software available than beos, purely because it has a much wider user, and therefore developer, base.
your windows only programs will not run natively under linux. there are two problems with this, the graphical environment in linux is totally different from the one in windows, so any programs using a graphical user interface need the graphical parts of them rewritten if they want to run on the other, the second problem is that this is totally impossible to do with closed source programs. most programs for windows are closed source, for a number of reasons, largely historical, while probably a majority of linux programs are open source (meaning anybody can edit the program code, recompile it on their machine and run it again, eg to get it to work better, or with your hardware or whatever).
BUT there are a couple of projects, most notably one called "wine" and a derivative called "winex" that attempt to translate all communication between your windows program and your linux system so the program thinks it is running under windows and your system thinks it's running a linux program. your mileage may vary here, i have always found this method to be slow, buggy, unreliable and pointless. i would *strongly* recommend finding alternatives to your programs that run natively under linux, or keeping windows on your computer to reboot back into when you need to use those programs. and if your computer is that old, i suggest you make it windows 95 on that partition right enough (or 98 if you are really insistent).
There's a lot to decide when installing linux, first which linux vendor to get a distribution from (a distribution is a complete system plus applications packaged up in a hopefully nice way). There are many. All are hugely configurable, and most have unique ideas about how the default configuration should go, so depending on what you want, and what they think you should want you could spend a lot of time, or not much time, configuring your system to your comfort. the internet will help you with this, trust me.
I would recommend red hat (recent versions known as fedora) or suse as your linux version, close runners up include mandrake, or if you don't mind using a slightly off the normal track linux then i might suggest slackware or xandros. it's a good idea to get a knoppix disk too, this is a bootable linux system on a CD, which you do not need to install but can run right off the CD. this has its advantages and disadvantages. i have never really needed one, but as a new user you might get use from it to familiarise yourself with the system and its gui.
you also need to think about partitioning. this is usually easy with the installers of distros such as fedora, suse and xandros etc, but you do need to know, generally speaking, what you are actually doing before you go ahead and have a go. also, back up your stuff first. honestly, back it all up. yes all of it. i mean it.
now, you are going to have to put in some time figuring out how to customise your new system. i am still learning after several years. everything (more or less) is customisable in a linux system, so be prepared for it to be a lot more involved than using windows. i usually recommend this enormous tome for people unused to a unix environment. it contains information on everything you need to know about unix systems:
http://docs.rinet.ru:8083/UNIXy/your questions about windows emulation, and others about windows filesharing are not covered there, but they tend to be the sort of thing you'll get answers about on forums.
good luck, post again if req'd and have a nice linux!
