does he have the basic run time files?
does he have the controls?
like if you use the richtextbox you must copy that dll to the users computer
this is from my installer
[Files]
Source: "C:\00 - MJ Plug-Ins\Cover Art Finder\Cover Art Finder.ocx"; DestDir: "{app}"; Flags: restartreplace regserver
Source: "c:\Windows\system32\mscomctl.ocx"; DestDir: "{sys}"; Flags: restartreplace sharedfile regserver
Source: "c:\Windows\system32\msstkprp.dll"; DestDir: "{sys}"; Flags: restartreplace sharedfile regserver
Source: "c:\Windows\system32\tabctl32.ocx"; DestDir: "{sys}"; Flags: restartreplace sharedfile regserver
Source: "c:\Windows\system32\comct232.ocx"; DestDir: "{sys}"; Flags: restartreplace sharedfile regserver
Source: "c:\Windows\system32\Richtx32.ocx"; DestDir: "{sys}"; Flags: restartreplace sharedfile regserver
it also installs the basic vb6 runtime files
; begin VB system files
; (Note: Scroll to the right to see the full lines!)
Source: "c:\vbfiles\stdole2.tlb"; DestDir: "{sys}"; Flags: restartreplace uninsneveruninstall sharedfile regtypelib
Source: "c:\vbfiles\msvbvm60.dll"; DestDir: "{sys}"; Flags: restartreplace uninsneveruninstall sharedfile regserver
Source: "c:\vbfiles\oleaut32.dll"; DestDir: "{sys}"; Flags: restartreplace uninsneveruninstall sharedfile regserver
Source: "c:\vbfiles\olepro32.dll"; DestDir: "{sys}"; Flags: restartreplace uninsneveruninstall sharedfile regserver
Source: "c:\vbfiles\asycfilt.dll"; DestDir: "{sys}"; Flags: restartreplace uninsneveruninstall sharedfile
Source: "c:\vbfiles\comcat.dll"; DestDir: "{sys}"; Flags: restartreplace uninsneveruninstall sharedfile regserver
; end VB system files