Hi,
2.5 beside 2.0 is not possible.
But, if you follow this
Installing a new release of WAMPServer, you will not lose any of your local site and your database and you will have the opportunity to be able to come back to your 2.0 version at any time, with a few simple and quick handling.
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Documentation Apache -
Documentation PHP -
Documentation MySQL -
Wampserver install files & addons