javac is not recognized as an internal or external command in windows

Follow these steps:

Open my Computer.
Go to program files - x86 (if applicable)
Find "java"
Open it and select jre(yournumber)
Select Bin.
Click the bar up the top, You should see something like this: C:Program Files (x86)Javajre6bin
Paste that into notepad, as you need it soon!
Open the start Menu.
Right click Computer.
Select Properties.
Click "Advanced System Settings"
Click "Environment Variables"
You'll see two Boxes (if not close and follow the instructions again) in the top one Select "New..."
in Variable Name type "PATH" (it must be PATH and not PaTh/Path/pATH.. etc)
In Variable Value, get that thing in Notepad you Pasted in and paste it there.
Press "OK"
Press "Apply"