CAB files to IMF files somethings wrong

I use Incredimail for scrolling letters, we make the letters and compress them to a cab file and then change the file extension to imf so we can use it in our email. I have been doing this for about 4 years and suddenly it won't lose the cab extension so the letters don't work as an example it looks like this...

adayathebeach.imf.cab

I discovered this and I'm not sure how to get the cab extension off it....anyone have any idea's?\

Thanks in advance,

Icey

Hi Ztruker,

Thanks for your reply on this, this is a new install of windows 7 and I just went and did exactly what you suggested and then found your email...I have been using this particular system for months and I'm not sure what changed it but, got it now and it works just fine...sometimes it's the simplest things we overlook. \
Thank you for your reply and instruction.

Icey