compiling from prompt --- absolute beginner

Hi all, I really am perplexed by this issue, but it's the kind of
problem whose answer will probably jump to my face...

Ok, so I am under WinXP Pro, and I set up the following environment
variables:
SET PATH = %PROGS%\Java\jdk1.5.0_07\bin;%PATH%
SET CLASSPATH=.
I am playing with a small program that uses the standard class Point
somewhere. I do "import java.awt.*".

The code is located in the folder "C:\(...)\My Documents\Java
Projects". I can successfully compile with a simple "javac
SampleApp.java" at the prompt (from the same directory, obviously). I
repeat, it works just fine.

Now I moved the very same "SampleApp.java" to a subdirectory:
"C:\(...)\My Documents\Java Projects\Sample". When I try to compile
from that directory with the same command "javac SampleApp.java", I get
a "cannot find symbol" error:

SampleApp.java:13: cannot find symbol
symbol : constructor Point(int,int)
location: class Point
Point p = new Point(10, 15);
^
1 error

....and I have no clue... Help will be much appreciated!

.