Assuming the MYSQLServer from the old WAMPServer will run in your new OS you can do this.
First ensure XAMPP is stopped, and make sure its Apache and MYSQL services are stopped.
Launch \wamp\wampmanager.exe
Using the wampmanager menus do
wampmanager -> MYSQL -> Service -> Install Service
This should install a service called wampmysqld
or wampmysqld64
if you were running a 64bit WAMPServer, and the old MYSQL version will now be startable.
wampmanager -> MYSQL -> Service -> Start Service
You can now do a backup of your old database(s) using the command line tools like mysql.exe
or mysqldump.exe
If you wanted to get the old WAMPServer running you could also do
wampmanager -> Apache -> Service -> Install Service
wampmanager -> Apache -> Service -> Start Service
And you would have your old WAMPServer up and running exactly the way it was.
Possible issues:
If you do not have all the necessary MSVC runtime libraries installed restarting Apache may not work. But these can easily be download and installed. See POINT 20 on the troubleshooting guide on the WAMPServer forum There are links on that page that will help you download them all for 32 and 64bit systems.
Remember if you run 64bit Windows, you need to download the 32bit AND 64bit versions of the MSVC runtimes
You might have to download the MSVC 2008 32bit runtime to get wampmanager to run.