I'm trying to run my own server, but whenever I run "start server.bat" this comes up:

Exception in thread "main" java.lang.NoClassDefFoundError: com/mojang/minecraft/
server/MinecraftServer
Caused by: java.lang.ClassNotFoundException: com.mojang.minecraft.server.Minecra
ftServer
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: com.mojang.minecraft.server.MinecraftServer.  Pro
gram will exit.
Press any key to continue . . .

I've already googled it and searched the official forums and here. From the looks of it, a lot of people are having this problem, but nobody has been able to solve it. I'm pretty sure it's a java problem, but I don't know what the problem IS, specifically.

I've already posted on the official Minecraft servers, nobody there was obliged to help me. Please, if you know the answer to this problem I'd love to hear it! I've been at this for over four hours to absolutely no avail.

I've reinstalled Java twice, tried deleting and reinstalling the www.minecraft.net folder, restarted my computer, port-forwarded, let the ports through my firewall, and set my CLASSPATH to ";C:\Program Files\Java\jre6\bin".

PLEASE HELP!! I'm desperate! Thank you in advance.

EDIT: I just tried running the server on my desktop and it works fine, so it's got to be something within my system. I'd still like to get this figured out if possible, because I've got everything set up on my laptop already.