suddenly lost an application; plus, can't download anything

My brother's computer suddenly lost all traces of one of his installed applications. Not only is it no longer installed, but the executables and associated folders have all vanished, even when searched for with a file recovery utility.

Also (and I don' think this is a coincidence), suddenly he can no longer download ANYTHING, although he can receive email via Outlook.

We ran a security software scan, and no malware was found.

I'm mystified. Any ideas?

He's running Windows 7 and Mozilla Firefox.

 

Hi DavidGP -

Step 4 of MajorGeeks' Malware Removal Guide says to disable any disk emulation software.

I don't know anything about disk emulation software, but I can tell you this:

My brother was running the now mysteriously disappeared program (FloorPlan 3D) under Windows XP Professional, since FloorPlan 3D is an old program that won't run under his OS, Windows 7. In order to make that work, he ran Windows XP on a virtual machine created by Oracle VM VirtualBox Manager (version 4.2.14). Therefore, Windows XP appears to be running on virtual drive Z.

Is VirtualBox disk emulation software? If so, I'll disable it with DeFogger.

Incidentally, since DeFogger runs under both Windows XP and Windows 7, it can run in both 32-bit and 64-bit environments, right?

My brother's Windows 7 has Service Pack 1.

His current security software is StopZilla AVM 2013 (product version: 6.0.0.0, file version 6.0.3.61), and of course Windows Defender and Windows Firewall.

Since StopZilla and Defender are both installed on my brother's machine, I guess one of them will have to temporarily go away. I'm pretty sure both of them allow real-time protection to be disabled, but that's not sufficient; I'll have to actually uninstall StopZilla, right?

Full scans done by both StopZilla and Defender found no threat.

Thanks for your help.

 

Hi DavidGP -

My mistake, I didn't realize that Windows 7 could run on a 32-bit machine as well as a 64-bit machine. My brother's machine is a 64-bit, though (AMD Athlon II X4 640).

BTW, my brother's edition of Windows 7 is Professional.

 

I was able to put Defogger on the desktpo and keep it there by disabling real time protection in StopZilla.