I'm amazed that you stuck with ME for so long. It actually went out with button up boots. Besides that, it was noted as being Microsoft's biggest lemon and the most unstable OS of the lot. I used it so I can vouch for all of that plus more. We called it the "Blue Screen of Death!"
However, the fact that your computer has ME, also means that your computer is very old. I'm amazed that GIMP even works, but lucky you.
May I suggest that before taking the plunge, you do one of two things.
1. Wait a year for Google Chrome OS which will be free and probably work with most Windows (pre Win 7) stuff okay after it's been out for a while. It's also linux, so it should work out of the box with GIMP.
2. Don't delete ME just yet because Linux may be too difficult to get your head around. Instead, download and install a CD version of Knoppix. It's free, boots your computer and runs Linux, but also leaves ME totally intact in case you want to go back. You just take the CD out of the drive, reboot your computer and it's back to normal
Sorry I don't have a link, but just Google Knoppix. If you like what you see, PM me and I'll send you a tutorial I wrote some time ago explaining how to install and run it. That goes for anyone else reading this post.
If Knoppix is too big to download, you can purchase a CD for about ten bucks. Either way, you get a bucket load of free software including Open Office and maybe even GIMP. You'll also be amazed at what else runs under Linux. That includes most Windows stuff if you install a plug-in.