MySQL server installation file download for windows
There is a "portable" ZIP package of version 5.6.27 (not 25) for download:
http://dev.mysql.com/downloads/mysql/5.6.html#downloads

For completeness, to install and run the server using an unprivileged account:


unzip 
rename my-default.ini to my.ini 
update base and data directory path in my.ini (data directory must exist) 
Open a command window in the installation path.
run the server once with ".\bin>mysqld.exe --log_syslog=0 --console --standalone --initialize" to set-up a fresh database (note: --initialize might be --bootstrap in that version) 
run the server with "mysqld.exe --log_syslog=0 --console  --standalone" (--console only if you want the output in the terminal window)
enjoy :)


"mysqld" can be installed as a background service (d for daemon), but you cannot do this without admin rights.