@raphoenix: Yes, you can always disable the security features of any Operating System.
You can disable UAC in Windows Vista and Windows 7 just as you can run as enable the superuser (root) on Ubuntu and use it all the time.
It's just a horrible idea if you want to protect your system from being infected by sneaky malware.
The best alternative to use if you find the prompts annoying is to disable the prompts and have UAC automatically elevate programs that need it. This is similar to configuring Ubuntu to always elevate to the superuser instead of prompting for a password. It’s much safer than running as the superuser all the time but still not the best thing to do.
The reason the current Windows Vista UAC prompts are more annoying than other Operating Systems like Ubuntu is mostly due to the Operating System's software environment.
Software for the UNIX environment has been programmed to support the concept of a low privilege user for everyday tasks and a superuser for Administrative tasks for at least the last 25 years (probably longer but I don't know the exact amount of years)
Thus most all of UNIX’s software environment contains software that works with the concept of least privilege as it’s needed.
When the Linux kernel was developed in 1991 by Linus Torvalds, it was designed to be UNIX-Like so it had all the great ideas from UNIX like least privilege that were basically free (Free as in Linus Torvalds didn't need to come up with the ideas, just coded them into a new kernel).
I don't know much about pre-Apple OS X versions but I do know that OS X has a very similar history, only I think that OS X actually uses a real UNIX kernel.
Unlike Apple, Richard Stallman (Started the GNU Project, See http://www.gnu.org/philosophy/.....eedom.html for how it relates to Linux) and Linus Torvalds, Microsoft decided they would just build their own Operating System not based on UNIX in any way; so all the features including least privilege have to be re-implemented for usage in Windows where Linux and OS X got their security features for free in a “the implementation is done so only the actual code needs to be written” way which is easier then the coming up with an entirely new implementation.
Microsoft for a long time has had a totally different view on how security should be implemented; they assumed that most computer users would find security systems like UAC annoying and made all user accounts on pre-Vista systems have full Administrator access by default where any running program can do anything including install a rootkit if the program wants to do so.
Microsoft has since found out that users will be even more annoyed by amount of malware that gets onto their systems so they created User Account Control (UAC) to be the best of both worlds, it has the security of a least privilege system but the convenience of a one click prompt to allow Administrative tasks.
The problem with it at the current is that the software developers for the Windows platform were not prepared for this*, many developers still thought writing the configuration for their software to C:\Program Files or C:\Windows was a good idea when Microsoft has been recommending against this in their guidelines for writing Windows XP compatible programs from the start for Windows XP, which left developers with plenty of time to make compliant software but like with the driver problems, the developers just kept on writing programs that worked on Windows XP but it was against the guidelines.
Thus when programs do things like that they were not suppose to be doing in the first place, UAC attempted to gracefully handle it by with things like redirecting writes to the VirtualStore folder but that didn't always work correctly so it will prompt for Administrator access because the program wants what it never should have needed.
Hardly anyone seemed to even try to figure out the perfectly logical reasons behind it before going to their favorite web site and complaining about the prompts.
Also UAC goes even farther than any UNIX-Like Operating System for privilege separation by providing what are called integrity levels. You can check out the article at http://www.securityfocus.com/infocus/1887 for more information on them. The really good thing is the Low Integrity Level, Internet Explorer 7 in Windows Vista will render all Web Pages there so should any security hole be found, it can’t do anything beyond screw up a couple minor things writable by that Integrity level (It pretty much just boils down to the C:\Users\[User Name]\AppData\LocalLow folder only).
For that reason alone, UAC makes Windows Vista and Internet Explorer more resistant to malware. In fact more so then Mozilla Firefox but most people don’t seem to realize this fact.
Or they just don’t care. The Low Integrity Level still has read ability to read all files that the user can read. Thus it doesn’t stop any information theft via methods phishing. That is one of the reasons Internet Explorer 7 includes a phishing filter to warn people of it. Unfortunately, IE7’s phishing filter is not very good. IE8 is supposed to have a much better phishing filter and to my knowledge Windows 7 will include IE8.
* To be fair to other software developers, Microsoft still doesn’t follow their own guidelines** for Microsoft Office, Windows Live and many other programs unless it’s required for Windows Logo certification like UAC is.
** To be fair to Microsoft developers, they at least always follow what is required*** of a Windows software program.
*** To be fair to other software developers again, there are many that do follow the requirements too but they are usually developing a minor program that isn’t used by many people.