Java SE (Java Platform, Standard Edition)

I'll make this brief.I have a Windows XP Home operating system and I
downloaded the jre1.5.0_05 SDK.I wrote a simple "Hello World" program
and tried compiling it.
I got the standard 'javac' is not recognized as an internal or external command, operable program or batch file error,so I thought I'd find the proper file path
to Javac.exe.
The thing is believe it or not,Javac.exe appears to be nowhere on my computer.It's not listed in my java bin.I tried doing a search on my computer
and no javac.exe was to be found..
Should I just try installing java again?
Thank you