OK, so you've hopped straight on the OS X bandwagon - as soon as you possibly could, you installed the "world's most advanced operating system" on your Mac. Well done.

Problem: there aren't that many apps available just yet. Most of your old applications run OK under the Classic environment, but it's not as stable as you'd like. Games, especially, don't like Classic much. Most applications, in fact, run better under genuine Mac OS 9.1 than they do under Classic in Mac OS X. Being an early adopter is one thing, but you have work to do.

Well, you can just start up in Mac OS 9.1 (you did give yourself the dual-boot option when you installed, right?). You can leave Mac OS X installed on your computer but unused, waiting for the day your favourite apps finally arrive. But what if you need the drive space?

The good news is that you can completely remove Mac OS X reasonably painlessly, without disrupting your OS 9.1 setup. It just takes time, and it's a little fiddly. You'll also need to use ResEdit, but don't worry - it's not really a hack.

ON WITH IT

The first thing you need to do is to start up in Mac OS 9.1. Deleting Mac OS X while trying to run Mac OS X would be a fool's errand. Just switch startup disks using System Preferences, and restart.Next thing is to deal with the Users "folder, which will be in the root directory of your hard drive. If there's anything in there that you want to keep, such as work you've done in Mac OS X, dig it up and put it somewhere safe.

Then delete the following folders: Applications, Library, System, Users and Developer (if you installed the developer tools). Make sure, obviously, that you're deleting the Mac OS X System folder and not the Mac OS 9.1 one. You can tell which is which because the active folder has a Mac icon on it. Move the files called "mach" and "mach.sym" to the Trash. These files are the kernel of OS X, but as far as OS 9.1 is concerned, they're just files.

Then, empty the Trash. This will take a while, so perhaps you might want to get a sandwich or something. A fairly basic installation of Mac OS X includes tens of thousands of files, and if you've downloaded a few applications for OS X or installed the developer tools, it can get quite ridiculous.

Next is the part where you need ResEdit. If you don't have a copy, download one from www.resexcellence.com - it will come in handy. The reason you need ResEdit here is because some of the files you need to delete are invisible. Apple doesn't want people who don't know what they're doing to touch these files or even know they're there. But you are using ResEdit, so you must know what you're doing. Congratulations, you're a hacker.

Before you run ResEdit, open the root directory of your hard drive and leave the window open on the desktop. Move it to the far right of the screen so you can see it while ResEdit runs. Then start ResEdit.

From the File menu in ResEdit, select Get File/Folder Info and navigate to the root directory of your hard drive. You'll notice that certain files are visible in ResEdit that aren't visible in the Finder window. Open ".DS_Store" and a window should appear. Note that among the options in the bottom half of the window is an option labelled "invisible". Deselect this option and close the window, saving your changes. You'll notice, when you do so, that the file will appear in the hard drive's window in the Finder.

Repeat this process for any of the invisible files and folders with a full stop (.) at the start of their filenames, and also for the following: mach_kernel, Volumes, Network, tmp, etc, var, bin, private.

Then quit ResEdit. Back in the Finder, select all of the files you just made visible and drag them to the Trash (be careful not to lose anything you still need). Empty the Trash, and go get another sandwich.

Finally, open the Extensions Manager control panel and scroll right down to "the bottom, where it says "System Folder". "If necessary, click the triangle to get more detail. Then deselect "ProxyApp" and "Classic SupportUI"."And now your Mac is back to normal, with all the familiar bugs and quirks and no UNIX. Get on with your work and come back to Mac OS X when you, and OS X, are ready.