jar file not working in Windows 7

Hi,

The scenario is as follows:
I used to run a little jar file coded by me in XP, but now that I am using Windows 7 it doesn't work any more.
My java version is Version 6 Update 18

I get the following message:

Exception in thread "main" java.lang.NoClassDefFoundError:
Caused by: java.lang.ClassNotFoundException:
at java.net.URLClassLoader$1.run(Unknown Source)
...
Could not find the main class: C:\SMFilesGenerator.jar. Program will exit


I would appreciate it so much if you could help me.

Thanks for your reply
I tried moving it to 'My Documents' folder, but it is still not working. Today I installed the jdk-6u18-windows-i586, to see what happens, but there has been no change.
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