[plt-scheme] Unable to install DrScheme 202 on MacOSX system

Hi,

I installed the MzScheme on my Max OSX 10.2; and found out the DrScheme.
When I tried to install DrScheme it complained that there is a newer 
version installed and refuse to install.

I tried to remove the MzScheme at the following files as specified in 
the readme file:

	/Library/Frameworks//PLT_MzScheme.framework
	/usr/local/plt-202

And tried to install DrScheme again, but it still complained there is a 
newer version?

How can I uninstall MzScheme?

Thanks,
Alex