Admin account on WinXP Pro

I've read that I shouldn't be using the Admin account as my main account in WinXP. Is this really a big issue or just a precaution? Should I be creating another account and using that instead? No one but my family uses my machine, I have the firewall on, an AV running, and am careful about what I do and where I go. Do I have anything to worry about?
Umm why is this? I haven't heard that.. I have always been Admin on the comp and that is the only account on it too.

Win XP Home for me though.
I use Pro and am the admin.

If you know how to use a computer reasonably well, I see no reason for not using an Admin account
The risk of running as administrator is that if/when something does get entry to your machine (virus/trojan/whatever) it automatically has full access to your machine. Unfortunately there are tons of programs that are poorly programmed or made for Windows95/98/ME that won't work properly unless run as administrator.
So as long as I'm careful where I go and what I d/l I should be okay? I think I actually read this in the Windows Help and Support Center that's built in. I just got a little nervous after reading it. Thanks for the clarification!
It helps to be careful, but say there's a vulnerability in your IRC client or web browser or IM client or some coverdisk or commercial software has managed to get infected (happens every once in a while). In the Unix world, where these things have been worked on for a longer time, many software will refuse to run entirely if you're root.
one good helpful hint is to rename this account, because if the default is administrator, and someone is trying to hack into your computer they can guess administrator, and if you haven't renamed it they have half of the access to your computer... so renaming that acc is a good idea.. if you need assistance on how to do that just let me know.