Hmmm..... There are too many variables to give you a "pat" answer, or guarantee that Wxp will work on any particular amount of RAM, but I recommend 256mb. If I gather the gist of your question, in considering Linux you may want to consider that KDE and GNOME desktops will be most familiar to ex Windows users. These are full featured desktop ENVIRONMENTS and generally will run on 256mbRAM (512mb preferred). Xfce, fluxbox and others are more akin to window managers and will run on as little as 128mbRAM, but may be foreign to Windows users, so be aware of this. One of the first things you will want to do is decide which desktop environment you prefer and act accordingly.
Most distros will allow you to pick and choose the desktop you want, but for the new user I recommend sticking with the defaults.
Of course you should always check compatibility with your hdwr. Best way to do this is to run a Linux LiveCD.
Distros using lighter windowing environments are SAM, Tinyme, Vector (which hauls *ss) and Zen which run well on 128mbRAM. DSL and PuppyLinux will run on even as little as 64mbRAM, but the interface may be too foreign.
Distros using full featured desktops are PCLOS2007, Mandriva, Xandros, *buntu, , Mepis , LinuxMint, Suse, Kanotix, Fedora and CentOS, which are good distros for the newb in general order of ease for the new Linux user. ( I say general loosely).
The great thing about Mandriva, PCLOS and SAM Linux is that they provide a centralized GUI administration center that is very similar to the Windows control center.
I converted to Mandriva (upon which PCLOS and SAM linux are based) about 3 years ago and haven't looked back. There are tons of "trying linux tutorials" . Here is one spread out over several posts beginning with the second post here
hope this helps
Edited by Trio3b, 26 March 2008 - 11:11 PM.