[plt-scheme] Help

I am using DrScheme version 202, and try to use Jacal (version1b2) and SLIB version 2d4) on my Windows 98ME PC.
I have downloaded and installed today DrScheme in the directory c:\program files\PLT as suggested by the installation program
I have DrScheme running, with the language option "Big Scheme"
I have moved the slib directory under the c:\Program files\PLT\collects directory
I did the same for the jacal directory
Then I execute the following comands :
 (require (lib "load.ss" "slibinit"))     ; loads "init.ss"
 (slib:load "c:\\Program files\\PLT\\collects\\jacal\\math")
and I get the error : 
 Error: ";required feature not supported: " defmacro
What is wrong?
Thanks in advance for your help
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