There was an interesting post on this subject here

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In order to make these changes you will first need to find your Firefox Profile.

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1. Find your Firefox profile

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If you are running Firefox 2 this is an easy matter as you can use the Extension Open Profile Folder

Go Tools/Open Profile Folder and you should see the Firefox Profile that you are running.

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If you cannot use Open Profile Folder you will have to look manually for your Firefox Profile Folder.

The following chart should help you locate your Firefox Profile:

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So once you have found the Firefox Profile.

Go

Extensions

[email protected]

install.rdf

and Edit RDF File

In this line you will see the current Version you are running.

1.90

If you change the value to a higher number than any current Version, you will no longer be prompted for updates

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related post:
How to return to Fast Dial 1.x after running Fast Dial 2.x

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