i dont know what operating system my imac uses and i dont have an operating disk either. what should i do?

Hello,

It has either 10.4, 10.5, or 10.6, that are the only ones it can run...

http://www.everymac.com/systems/apple/imac/specs/imac_cd_1.83_17.html

Cheapest Install Disc would be 10.6...

Snow Leopard/10.6.x Requirements...

General requirements

* Mac computer with an Intel processor

* 1GB of memory (I say 4GB at least, more if you can afford it)

* 5GB of available disk space (I say 30GB at least)

* DVD drive for installation

* Some features require a compatible Internet service provider; fees may apply.

* Some features require Apple’s MobileMe service; fees and terms apply.

Buy Snow Leopard > http://store.apple.com/us/product/MC573/mac-os-x-106-snow-leopard

Call Apple Sales...in the US: 1-800-MY-APPLE. Or Support... 1-800-275-2273

Other countries...

http://support.apple.com/kb/HE57

It looks like they might still have it...

http://store.apple.com/us/product/MC573Z/A?fnode=MTY1NDAzOA

But I'm not sure it not more serious. 😟

Disconnect power cord & any peripherals, wait 30 minutes, plug everthing back in & try alt key or Shift key.

The Mac cannot find the OS. A few possible causes in order of likelihood:

1. fatal permanent failure of hard disk
2. corrupted data on hard disk
3. incorrect data in NVRAM
4. no compatible OS installed on hard disk
5. damaged electrical connections to hard disk
6. failure of some other part of Mac
7. missing hard disk

• We all hope it is not item 1.
• Try resetting NVRAM: http://support.apple.com/kb/ht1379
• Try safe boot: http://support.apple.com/kb/ht1564

If the above don't help please say what happens if you boot while holding command and s keys.

What other computer equipment do you have especially Macs?