Salut Marc,

There may be an easier way with third party tweaker, but this will do
it:

Copy the text below between the dotted lines, but not the dotted lines
themselves. Open Notepad and paste it in. Save the result in a
suitable location as recent.reg - making sure that the default .txt
extension doesn't appear in the file name.
Double-click on the saved .reg file to merge the contents.
Restart.

--------------------------------------------------------------------------

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies
\Explorer]
"MaxRecentDocs"=dword:00000004

--------------------------------------------------------------------------

In the above I have set the maximum number at 4. If you want a
different number change the dword value indicated, e.g 10 would be
dword:00000010
8 would be  dword:00000008
{count the zeros to make a maximum of 8 digits.