Some problem I encounter...
I decide to upgrade from 1.7.1 to 1.7.7
I have some problems and I worked most of them.
First if you decide to go for different path than C:\xampp, no matter what they say... HARD CODE your new PATH in my.ini (xampp\mysql\bin\my.ini) You will need to hard code basedir, tmpdir, datadir and if you don't use innodb you can uncomment skip-innodb and add default-storage-engine = MyISAM
*tmpdir has to be with "\\" (d:\\xamp\\tmp)
After you did that in order to start MySQL as service first you will have to remove any existing services of mysql after that open as administrator cmd(command prompt) type "yourpath\xampp\mysql\bin\mysqld --install"
this way you should add the correct path to you everything.
The only thing that I was not able to do is to make the control panel to read the proper my.ini file