I'm running PHP 5 solid, no problems. The only problem you will have is when you run it under IIS, instead of Apache... but that's an easy fix also.
Simply replace php5isapi.dll from final version with the one from RC2.
That should fix the nasty errors like:
"PHP has encountered an Access Violation"... damn MS.
To open a CMD window, press the Window Key + R.
Type [high]CMD[/high] and press Enter.
Type [high]CD C:\yourdirectory[/high]