How can I block an executable with a password?

Question

how can I block certain programs from opening without a password, specifically Firefox and IE? I'm trying to block internet (i.e. for free, w/o messing with network settings or using parental control programs)

Answer 1

for free, w/o messing with network settings or using parental control programs

This criteria really limits your options. You could make a second user account on the system and block access to the Firefox and IE binaries for that user completely. If you turn off simple file sharing (Windows XP method):

Explorer -> Tools -> Folder options -> View -> Uncheck "Use simple file sharing" and hit OK

You can then right-click firefox.exe and iexplore.exe from their installation location and go to the Security tab. If the specified user is already in the access list, you can simply deny them by clicking their name then clicking deny in the checkboxes on the bottom. If the user isn't in the list, click add and add them then explicitly deny them. In the end it should look like this for the user you are denying:

If they try to access one of the binaries they will get an error like this:

Windows cannot access the specified device, path, or file. You may not have the appropriate permissions to access the item.

Answer 2

Googling "application or software locking" says http://www.secretfilesoftware.com/lockanexe/

Not free but Invisible Secrets 4 has this feature

I like John's idea better though.

Answer 3

To block all Internet access for all programs, you could also install a firewall that demands a password for configuration change. That way you could lock all Internet access, requiring a password for unlocking.

The only free firewall I found that's advertised as using passwords is:
SoftPerfect Personal Firewall