Windows 8.1 (running in VMware Fusion 6) keeps resetting my default program associations after rebooting

I tried to set Google Chrome as my default browser in Windows 8.1 (virtual machine running in VMware Fusion 6) but somehow mysteriously failed over and over again.
According to Control Panel\Programs\Default Programs\Set Default Programs\Set Program Associations, there are 19 possible associations for Google Chrome:
Extensions: .htm, .html, .shtml, .webp, .xht, .xhtml;
Protocols: FTP, HTTP, HTTPS, IRC, MAILTO, MMS, NEWS, NNTP, SMS, SMS, SMSTO, TEL, URN, WEBCAL
I have no problem selecting some of them, or "set this program as default" so that "this program has all its defaults." (I am the only admin user, but not the builtin admin account.)
However, after restarting the VM, the program associations for Google Chrome will reset on its own. Specifically,
"this program has all its defaults" becomes "this program has 14 out of 19 defaults", losing the following five crucial protocols:
FTP, HTTP, HTTPS, MAILTO, NEWS
And these protocols simply hang there unassociated—they don't belong to IE either.
So I am extremely confused; how could the system reset my default program associations? What's wrong?
In case it is relevant, I will also post my VMware Fusion VM Default Applications settings here. All of the options are unchecked: "Open your Mac files and links using Windows applications"; "Open your Windows files and links using Mac applications";
"Run Windows applications from your Mac's Applications folder."
Thank you for your time.