I was recently given an iMac from a job I worked at as they had upgraded to a newer model.
I'm wanting to restore it so I can set it up for my own use.

The only downside to the Mac is that it has several user accounts (2 of which are password protected...the people who set these up no longer worked for the company thus taking their passwords with them) also, the Mac is partitioned and has Windows installed as well(it too with several users on it).

Whats the best way to reset the Mac to it's original state with no partition and no user accounts...or is that even possible?

It's an iMac with OS X
Specs are:
27-inch screen
3.1GHz Quad-Core Intel Core i5
4GB memory
1TB hard drive
8x SuperDrive (DVD±R DL/DVD±RW/CD-RW)
AMD Radeon HD 6970M graphics with 1GB memory

Built-in FaceTime HD camera

Thanks guys!

Download Mountain Lion from The Apple Store. Only $20.

The one thing to remember if you wipe the machine and install Mountain Lion is that you won't have the apps that come with a new iMac. ML doesn't install iMove, iPhoto, or iDVD. You can purchase all of them through the App Store, iPhoto is only $15 US. If you need iMovie or iDVD to process your video from a video camera those are able to be purchased too.

If you have the password for one user that is an admin you can delete the other users and set up a new user for yourself as admin. Then you can boot to that new user and delete the other admin.

Boot Camp will allow you to delete and resize the Windows partition so that it adds the Windows partition back to the main HD. http://www.simplehelp.net/2009/01/26/how-to-delete-a-boot-camp-partition/

Very nice! So better(and cheaper) to try and find an admin password first before re-installing...got it.

Thanks for the help!

You can reset the admin password with an install disc.

Just an FYI, you can't purchase iDVD through Apple anymore. You have to get an older version through Amazon.

But then again, who uses iDVD anymore?