Prevent Applications From Changing Extensions In XP

[Rez.]

Hi

I've been searching for awhile on a way to prevent various Applications from changing file extensions in XP.

So far, I've not been able to find anything and Gpedit has yielded little in control over Extensions. Is their perhaps a

Reg file or setting somewhere in XP that locks out HKEY_CLASSES_ROOT from being changed by applications?? I've only

found one piece of software on the Net called "Associate this" but it is payware (Something I'm not prepared for at the moment).

I really would like a built in soloution if there actually is one - Or perhaps a no bells freeware that prevents Apps from changing

extensions?? Any help would be appreciated ...

Thanks for reading.

PS: I'm using XP Pro SP2.