Downloaded Files Are Corrupted

Whenever i download a file such as .msi installer, .exe executable, or .zip archive with IE and run it, it crashes (not IE but the file that was downloaded.) This recently started happening on my Home Premium 64-bit Vista installation, and the problem remains after reinstalling Vista two times from scratch. If the file was downloaded on another PC and saved to a flash drive, it runs fine on Vista. I have tried the sfc /scannow command, as well as disabling any firewall, antivirus, etc. and changing the IE settings. This occurs on a clean installation of Windows Vista also. Here is the crash report, for example this time I was trying to install the FireFox installer after downloading it with IE:

Problem signature:
Problem Event Name:APPCRASH
Application Name:Firefox Setup 2.0.0.11.exe
Application Version:4.42.0.0
Application Timestamp:44e24a66
Fault Module Name:Firefox Setup 2.0.0.11.exe
Fault Module Version:4.42.0.0
Fault Module Timestamp:44e24a66
Exception Code:c0000096
Exception Offset:00003d99
OS Version:6.0.6000.2.0.0.768.3
Locale ID:1033
Additional Information 1:8d13
Additional Information 2:cdca9b1d21d12b77d84f02df48e34311
Additional Information 3:8d13
Additional Information 4:cdca9b1d21d12b77d84f02df48e34311Read our privacy statement: Microsoft Online Crash Analysis