Vista - how do i turn data execution prevention off?

How do I turn Data Execution Prevention off?
people keep telling me how to turn it off for a specific program. i dont need that. here's the problem: when i turn my computer on all thats on my desktop is the background. no start menu, no tool bar at all for that matter, no icons, nothing but the background. a box pops up that says that the "data execution program" is on. i close the box and nothing happens. still nothing on the desktop but the background. how to a fix this when i cant even get into the control panel or anything because its not there!!!!???

I can tell you how to disable DEP, but that does not appear to be your problem.
It appears you have significant Windows Corruption either due to malware/registry cleaner use/User error that only a reinstall of Vista may resolve.

let me ask you this:
What antivirus/antimalware program are you, or have you been running?
Are you using UAC, or have you shut it off?
Have you been using registry cleaners?

Scan/clean your system here:http://www.eset.com/onlinescan

Sorry if this is not what you wanted to hear. But this is how to resolve your issues.
Re-install, or insert your Vista disk (or boot into recovery partition) use the advanced recovery partitions to do a system restore to a date before the corruption/infection occured (if said restore point still exists). Otherwise, reinstall. If this corruption is due to a virus and/or Malware and you can resolve it with Restore utility. YOU MUST turn off and then turn on System Restore to completely remove the malware from your system.

Always use UAC, Install an excellent Antimalware program (I recommend NOD32 4.0) and use Windows Defender. DO NOT use registry cleaners as they often cannot distinguish between legitimate and unwanted entries, and more often than not, delete critical Windows entries (.dll) [svchost.executables] resulting in corruption and the need for Windows re-installation.

For futher info regarding Antivirus products and their performance:
Vista SP1 Antivirus Performance

For those looking to improve Vista performance and speed try this:
How To Make Vista more responsive and faster