Hi there
if you UPGRADE to W8.1 rather than clean install then the VMware adapter settings (ON THE HOST) get hosed up. Your VM's won't be able to connect to your network ( and / or the Internet too).
Either re-install the adapters manually - via the VMware program "Repair program" or uninstall VMware and install the latest version - in my case VMware workstation 10.0.1
I made another post about this in the Forum elsewhere.
I didn't encounter this issue when I upgraded my machine to 8.1 but I'm running VMWare Player. In addition, the first time I went to fire up Player, it prompted me to install a new version.
My VirtualBox VM's seem to be working fine after the upgrade.
Home built i7-8700K, Hp Envy x360 EVO Laptop, MS Surface Pro 7
CPU
3.7Ghz Core i7-8700K, 11th Gen Core i7-1165G7 4.7Ghz, 10th Gen Core™ i5-1035G4 1.1Ghz
Motherboard
ASUS TUF Z370-Pro Gaming, HP, MS
Memory
16G, 8G, 8G
Graphics Card(s)
AMD Radeon RX580, Intel Iris X Graphics, Intel Iris Plus Graphics G4
Sound Card
ATI High Definition Audio (Built-in to mobo)
Monitor(s) Displays
Dual Samsung U32J59 32 inch monitors, 13.3" display, 12.3" display
Screen Resolution
3840x2160 (Desktop), 1920x1080 (laptop), 2736x1824 Pro 7
Hard Drives
500GB ssd boot drive with 2 & 10TB Data (Desktop), 512GB ssd (laptop), 128GB SSD (tablet)
PSU
Corsair CX 750M
Case
Antec 100
Cooling
Coolermaster CM 212+
Keyboard
IBM Model M - used continuously since 1986
Mouse
Microsoft IntelliMouse
Internet Speed
665Mbps/15Mbps down/up
Browser
FireFox, MS Edge
Antivirus
Defender on all
Other Info
Retired in 2015 after working in the tech industry for 41 years. First 10 years as a Technician, the rest as a programmer/software engineer. After 1 year of retirement, I was bored so went back to work as a Robotic Process Automation Consultant. Retired for 3rd (and final) time in 2019.