Will I still be able to play Pirates Online when I install Ubuntu

http://piratesonline.go.com/welcome

? is this the game you play on line? or are you playing a game you installed on your computer?

You install on the computer

Yes, that is the game I play.

Users report that with recent versions of wine, this apparently works. I would recommend using a "try ubuntu" (liveCD) session first to confirm this, or installing ubuntu-on-windows (WUBI), so you can still go back to your windows install if need be.

http://appdb.winehq.org/objectManager.php?sClass=version&iId=10979&sAllBugs

Or try a virtualbox install :). Seems to say it runs..

Usually, playing game under a virtual machine (Virtual Box or VmWare) is too slow (when it works). You should try Wine first. Playing games is the remaining big issue with Linux.
To test with a Live session, you will have to make a bootable Ubuntu stick memory WITH persistent area to install on key Wine and PiratesOnLine.
Personally, for playing games, kept Vista and did a dual boot configuration (for other Windows software, I use Windows guest installed on a virtual machine on Ubuntu host and it works perfectly).

Thank you