Not valid Windows image

When trying to connect to broadband receive message stdialup.exe-bad image,
this is enlarged in window to 'The application or dll
C:\WINDOWS\system32|TAPI32dll is not a valid Windows image. Please check this
against your installation diskette.
Have tried system restore but this is also not allowed to complete a
restore. Also other exe files not allowed 'bad image' message received each
time. Do not have a usable disk to check files , how do I repair this, am
broke silver surfer.