Here's how you do it:
Using 64-bit internet explorer (firefox is only 32-bit, make sure you use the 64-bit shortcut in the start menu), go to Sun's Java download page. It should automatically detect that you're on a 64-bit OS and offer up 64-bit java. Run the installer, it should install into Program Files\Java by default.
Download the minecraft .jar file (listed under linux/other) from the download page. Also copy the command line options, you'll need that.
Create a windows shortcut to run minecraft. Set "Start in" to be where the .jar file is. I moved mine to c:\Users\Scare\Minecraft
Set Target to
"c:\Program Files\Java\jre6\bin\java.exe" -Xmx1024M -Xms512M -cp Minecraft.jar net.minecraft.LauncherFrameYou can also use Change Icon on it and select your old minecraft.exe to copy the program's icon.
If you want to add it to steam as well, you can point steam at the windows shortcut.
I haven't tried increasing the memory yet, but I think you can safely increase the -Xms parameter to something bigger.