Why can't I install/uninstall software despite being logged in as an Administrator?

Question

I am signed in under an administrator account in my laptop; however, now vista is not allowing me to install / uninstall any software.

Solution

Since you are running under your username with Admin privileges, Windows Vista does not really give you privileges to run stuff. To access the administrator account and install software and stuff you need to access the hidden "Administrator" account.

Go to the command prompt icon and right click and hit "Run as Administrator"

Type in the following command:

net user administrator /active:yes

Reboot your computer to apply the changes and you now have access to the real admin account.

To turn off this administrator account, run the same command but instead of yes, say no.

Comments

[Eyal]

We're definitely going to need more details than that in order to help you with your problem. What type of software are you trying to install/uninstall? How have you tried to install/uninstall it? etc.

[Admin]

Thank you Cody for your quick response. I was able to install any software before. Now I tried Firefox. I am not able to run McAfee virus scan

[Admin]

One more symptom is even though connected to electric power some times it is showing as though running on Battery.

[LawrenceC]

What happens (error messages, etc.) when you attempt to install software. Also, sounds like the power jack in your laptop has become disconnected from the board and needs to be resoldered, or your charger is bad.

[paradd0x]

@Razack Is the administrator account logged in as Administrator when you look at the account name? Or is it your name with Administrator privileges?

[Razack]

@klutch2 My name with Admin privilege

[Razack]

@ultrasawblade asking for more credential

[LawrenceC]

Is your laptop part of a domain (Start -> sysdm.cpl [Enter] -> if it says anything about Domain on that screen, then you are)? If so, you might need domain admin or similar credentials to install software.

[paradd0x]

When you are under your name with with Admin privileges, that is just a gimmick. Vista does not give you real privileges. The real Administrator account and privileges are hidden. You need to enable that account to fully control your computer.

[kreemoweet]

This answer is completely incorrect. Every administrative account has full admin privileges. There is no need whatever for the builtin Administrator account. The question asker (and others) need to learn about Vista's User Account Control and its Admin Approval Mode.

[Thalys]

Apparently this worked for the OP. However, feel free to post a better, more detailed answer, referencing this answer and why its incorrect, both so that you can set the record straight properly (and get some reputation in the process!) and so that others can benefit from the explaination.