OK, It's common error with IIS. Read the following instruction by Martin:
For example: Not Found: The requested URL /moodle/file.php/2/myfile.jpg was not found on this server.
A common symptom is that user profile images/> don't display properly.
How to fix under Apache:
Your web server needs to be configured to allow the part of the URL after a script name to be passed directly to the script. This should be enabled by default in Apache 1, but is usually disabled by default in Apache 2. To turn it on, add this line to your httpd.conf, or to a .htaccess file in your local directory (see the Install documentation for more details):
Note, this will ONLY work for Apache versions 2.x.
How to fix under IIS:
You need to enable the setting AllowPathInfoForScriptMappings. See this Microsoft Knowledgebase article for more information about how to do this.
Workaround in Moodle:
If for some reason you are not able to fix this problem properly as above, then you can switch Moodle to use an alternative method. The disadvantages are a slight loss of performance for your users and you won't be able to use relative links within HTML resources.
To use this alternative method: login as Admin, go into the "Configure Variables" page and change the setting for "slasharguments/>". You should now be able to access your uploaded files/>.
I hope it's OK