Microsoft Windows

I have never heard anyone pronounce Microsoft or Windows incorrectly. Everyone pronounces it as "mike roh soft win doze".

Mac OS

I have never heard anyone pronounce this incorrectly. Everyone states it as "mack oh ess". So if you’re talking about Mac OS 9, it’s "mack oh ess nine".

Mac OS X

Tons of people get this incorrect, both in writing and speaking. In writing, some miss the space and write OSX when it should be OS X. And yes there is a space. Proof is on Apple’s Mac OS X web page. Look at the title bar of your browser.

In speaking, some say "oh ess ecks" when it should be "oh ess ten". Many do not know the X is actually a roman numeral ten. Why ten? Because OS X was the release right after OS 9. Why X and not 10? It could have very well been inspired from Jobs’ prior company, NeXT.

Linux

The Big Question: Is it pronounced "line-ucks" or "linn-ucks"?

Answer: Linn-ucks.

How do I know this? Linus Torvalds said so. Watch this video and listen to the last part where he says "..but Linux is always Linux". He pronounces it as "linn-ucks".

Case closed.

Ubuntu

I pronounce it as "oo-boon-too". So does this guy. Sounds correct to me. Some say "oo-bunn-too" or "yoo-bunn-too", but it’s "oo-boon-too" for me.