Using Time Machine and other uses on one drive

Question

I want to get the Iomega Prestige 500 GB USB 2.0 Desktop External Hard Drive 34270 to back up some files from a Tiger machine, and possibly from some Windows machines to, but I also want to be able to use it for Time Machine in the future.
How do I format the drive for Time Machine? If I format it after I start putting files on, would the files be removed? If it's formatted for Time Machine, will it work with the Windows computers? If formatted for Time Machine, will I be able to use it for Time Machine AND regular file storage?

Answer 1

Prepare the drive as follows:
Extended Hard Drive Preparation
1. Open Disk Utility in your Utilities folder. If you need to reformat your startup volume, then you must boot from your OS X Installer Disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Installer menu (Utilities menu for Tiger or Leopard.)
2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Note the SMART status of the drive in DU's status area. If it does not say "Verified" then the drive is failing or has failed and will need replacing. SMART info will not be reported on external drives. Otherwise, click on the Partition tab in the DU main window.
3. Set the number of partitions from the drop down menu (use 1 partition unless you wish to make more.) Set the format type to Mac OS Extended (Journaled.) Click on the Options button, set the partition scheme to GUID (only required for Intel Macs) then click on the OK button. Click on the Partition button and wait until the process has completed.
4. Select the volume you just created (this is the sub-entry under the drive entry) from the left side list. Click on the Erase tab in the DU main window.
5. Set the format type to Mac OS Extended (Journaled.) Click on the Options button, check the button for Zero Data and click on OK to return to the Erase window.
6. Click on the Erase button. The format process can take up to several hours depending upon the drive size.
Now, you cannot use a Mac formatted drive with Windows unless you install Windows software that enables this such as MediaFour's Mac Drive.
If you format the drive FAT32 instead of Mac OS X Extended then you can use the drive on both the Mac and Windows without anything additional, but the drive will not be usable with Time Machine unless it's formatted Mac OS X Extended.
Now, you can partition the drive so that one partition is formatted for OS X and the other for Windows, but to do that you must partition the drive using GUID instead of APM. The former is not compatible with Tiger or non-Intel Macs.
Note that to use Time Machine you must upgrade to Leopard. TM is an incremental archiving backup program so your backup drive will need to be at least twice the capacity of the drive you will backup.