NB: I have an expanded (160 MB RAM) Rev A (Bondi Blue) iMac, running OS8.6 with iMac update 1.0 and the firmware update installed. I have not installed any modem or CD updates and not expanded the VideoRAM.

My iMac crashed all the time when I first had it, on one occasion in Outlook Express which trashed my hard drive. At the time there were no external storage options, so I had no way of backing up. I had to reformat the hard drive and, of course, lost all my data and had to reconfigure my internet account. It crashes much less often now, but the side cover is usually off and I still keep a pile of paperclips by my iMac.

The Emergency Handbook that came with RevA iMacs (and was my guide in moments of crisis) has been renamed the 'Troubleshooting Handbook'. It has been revised and can be found online at http://til.info.apple.com/techinfo.nsf/artnum/n43050, although if you need to refer to it you probably don't have access to the internet! Probably worth a browse, though, but bear in mind this information relates to MacOS in general and is not iMac-specific.

In some of my nerdier moments I've been fiddling with emulators with varying luck. Emulators are programs which emulate other computing platforms, usually old but much loved ones.
MacSpectacle 1.8.2, a ZX Spectrum emulator, seems to work but sadly ZX Loader (which lets you play programs off cassette tape into your Mac!) does not - it only works at 22kHz, and as far as I can tell the iMac's sound card only supports a 44.1kHz sampling rate.
I've also failed to get Vectorama 1.0.2 to work - it emulates classing vector-based arcade games like Asteroids and my personal favourite Battle Zone. The program seems to run OK - apart from the fact that I just get a black game screen with nothing happening... either I'm doing something stupid or there is a conflict or compatibility issue.
A huge list of emulators can be found at http://www.komkon.org/EMUL8/Macintosh/

Peter Jones reports that he couldn't get iCAB to work - iCAB is a small web-browser for the Mac that is under 2 Megabytes. I managed to install it OK, and it would let me browse local files (on my hard disk) - however, when I went online I found it painfully slow and it would often fail to load pages that appear in Netscape Communictor in seconds. Which is a shame, as the program looks very nice and the idea of a slim web browser is a great one. The preview version is downoadable from http://www.icab.de/download.html...

I found setting it up for my existing Demon internet account fairly easy - Demon's helpdesk talked me though it and only told me one wrong thing which I spotted and fixed myself. Considering this was the very first day the iMac was released, I was fairly impressed, but it's nowhere near as simple as the "there is no step 3" TV ad suggests! My iMac's modem typically runs at 43000bps into Demon's main 0845 number, and the iMac is at the end of a long run of phone extensions in my house.
Setting up my mother-in-law's LineOne account was even easier, using the setup assistant provided.

I got a copy of LinuxPPC from the States, but the readme said it wouldn'r run on an iMac because it had no USB drivers - and no USB, no keyboard and no mouse! But at http://w3.one.net/~johnb/imaclinux/ you can find details of how to get LinuxPPC running on your transparent machine. And there are some cute animated GIFs of penguins as well, of course... Personally I'm just happy my iMac is working OK at the moment and won't be meddling with partitioning hard drives thank you very much.

MacOS spoke to me! A demo of the excellent vector graphic shoot-em-up Battle Girl spectacularly crashed - I did a apple-option-esc type of quit thing and then tried to switch the machine off using the power button on the main iMac unit. From nowhere a voice said something like "I'm sorry I cannot perform that action as the shutdown procedure is already in progress" - shades of HAL in 2001 or what?! I half expected it to start singing 'Daisy' and telling me that turning the power off really wasn't a very good idea...

Beware of old versions of Norton Utilities - if they're not compatible with OS 8.1 or OS 8.5 it will trash your hard drive - and if you're trying to run Norton I assume you have enough hard disk problems as it is!

I had problems getting the RealPlayer to work. My first installation off the Real website seemed to work, but neither web browser would recognise it. I have since tried installing it off a MacFormat cover CD and it always crashed the iMac at exactly the same point in the installation procedure. However, I then installed Netscape Communicator which seemed to have its own plugin for RealAudio which works fine.

Doing a clean install now is a nightmare as I struggle to keep track of all the upgrades. I have done the iMac update 1.0, but NOT the CD update or the modem update - I read that a user in the US found his modem was trashed when the update when wrong, and as there doesn't seem to be anything wrong with my modem, I can't see the point in doing this potentially fatal update.
Prior to installing OS 8.5 on my RevA iMac, I bit the bullet and performed the Firmware update - the scariest 5 minutes of my life as a power cut or system crash could render my motherboard useless. I read somewhere that a UK user's keyboard and mouse stopped working after the firmware update, but I seemed to have no problems. My modem, Outlook Express, IE and Netscape Communicator all seem to work, but I've been so busy making new desktop themes that I haven't used any other applications or peripherals since updating the firmware.