I have a backup of windows vista as an ISO image on my computer but what can i use to put it on DVD so that i can use it when booting my PC up? I have tried Nero but i have no idea where to go on. Any other applications i can try?

Nero can easily do it. It's simple too. Just run the Nero Burning Rom software.
 
Click Open, then select the ISO file you want to burn and click open.
 
On the top menu bar select the target drive, or the drive you have your blank DVD disc in.
 
Then once again look on the top menu bar for the Burn button. Click it and your good to go.

If looking for a free version I would go with DeepBurner.
http://www.deepburner.com/

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E2180 @3.2Ghz + P35DS3L +8400GS (700/475 OC)  

AstroBurn is a pretty decent easy to use (free) burning suite.
http://www.astroburn.com/home

Although, if you already have nero... I would just stick with that.

On another note... I really wish windows had an .iso burning utility. It can already author DVDs :|

I opened Nero Burning ROM and dragged it into the window and i get this message:
 
"The file is larger than 2GB and therefore cannot be stored in an ISO file system. Please use the UDF file system to write such large files. This can be done by selecting another complication type."
 
I have no idea how to do this.

 
If you already have the iso, open nero burning rom, then click file->open.  navigate to where the .iso image is located, click it, then hit open.  It will immediately launch the burning "wizard" to start the burn.  You cannot drag and drop the .iso file to a dvd to burn the iso image (it's contents), it will (if using UDF) simply burn the one .iso file on the disc but then it will not be bootable.

Try IsoBuster..
 
Thats what I use,a nd it works great~

 
Nero has some updates that should fix this issue.  I know that I usually use Nero6 Pro, and have to install an update pack before it likes to play with my burner and DVDs.  I think it actually doesn't make a .ISO...its an MDF file.

I just created put the ISO file on disc the way gwolfman said but now i have another problem. I put it in my drive and reboot my PC and i press F8 to get the option to boot from disc. I choose my disc drive and then i get a message saying "press any key to boot from CD" , so i press a key and then my PC just boots up as normally.

How many ROM drives do you have? If you have two, you need to make sure you put the disc in the one that is set as the Master Drive. Or the one you set to boot from in the BIOS.
 
Assuming you have two ROM drives, it's possible that your putting it in the Slave Drive.
 
So I guess the first thing that needs to be answered is; do you have two ROM drives?

dude you need to burn the .iso as an image file.
 
The simpliest way to burn an iso is a small program called imageburn. All its used for is burning iso files.
http://download.imgburn.com/SetupImgBurn_2.3.2.0.exe

Yes i have two ROM drives, but when i pressed F8 it let me choose which drive and i choose the correct one.

Hmmm...that's odd. If you have that option it should work. I'd suggest trying it in a more basic way. Go into your BIOS and check which Drive is the Master or Primary Drive. Put the Disc in that one. Also, while in the BIOS go to the Menu that lets you select the BOOT Device order and put CD/DVD Drive as number one if it isn't already. Then Save and Exit and don't push F8, just let it go on its own and it should come up with the "Press any key to boot from..." screen which at that point you push any key.
 
If it still doesn't work, then there are two possibilities.  
1) Something went wrong when burning the ISO to Disc. (You might try burning the ISO to another disc and using that one. Make sure that you select to "Finalize the Disc" in the Nero Burn options.)
2) Your ISO is bad, which means you need to create a new one. Make sure it includes the files needed to make it a bootable disc.

Just tried making the disk drive the first boot priority and i think i know what the problem is. I decided to put my original vista disc in and i still had the same problem. It is because my keyboard only half works when booting up. When i got to the message "Press any key to boot from CD" , no keys work on my keyboard so it just passes that part and goes to the boot manager as normal. On the boot manager it asks me which hard drive to boot from but my keyboard does not work there either so i always have to wait the 30 seconds until it selects default.

The strange thing is that my keyboard works in bios and my keyboard works when i press F8 and DELETE, it just does not work on the boot manager and on the screen where it says "Press any key to boot from CD".

Any ideas on why my keyboard is doing this? The model is Microsoft Reculsa. Is there a way to boot from the CD without getting the "Press any key to boot from CD" screen?

I just did this myself using a DVD-RW and ISO Recorder. I own Nero 6 UE, but trying to figure out how to burn an ISO with was too convoluted.

 
yeah ditto.. Nero use to be cool and work nicely... then i think someone bought them out or something happened.. now its just too flashy trashy..  
 
for making cds/dvds i use CD Burner XP.. ( http://cdburnerxp.se/ ) its free and quite easy to use.. and enough features to keep most happy.. been using it since before the software even burned dvds.. actually switched to this after nero..