Trying to download Maverick, and keep getting "an unknown error has occurred'

It's a sign from God, leave well enough alone for now.

Have you not seen the Threads re data loss on external drives when upgrading to Mavericks?

I would check your Apple ID and password to make sure they are correct.

There could be a problem if you are trying to use a different Apple ID than the one which was used to install the current OS that is on your mac, for example, if you bought someone else's mac, and kept their OS on it, but now you are trying a different Apple ID.

Also I'd make sure that the current OS and the mac itself are compatible with Mavericks.

What is the current OS, and what mac is it?

Another possibility is just that the Apple servers are very busy as so many people are trying to download Mavs. If there's no other cause, then maybe try again later.

Just saw the post from makras.

There are always a few problems with a new OS. Apple can't police every maker of crapware that's on the planet.

If you have a WD external drive, I would transfer (not clone) the files from it to another non-WD external drive that doesn't have crapware on it, and then erase the WD drive, and then never ever again buy a WD drive.

You will find many posts on the Apple Discussions from disgruntled narcissists (a few borderlines too) who blame Mavericks for their computer problems.

Mavericks is excellent (at least for me).

Every new OS has some incompatibilities with older software. That's why if someone is an early adopter, they should understand this, and if they have a low tolerance for frustration, or are uncomfortable with basic mac maintenance and troubleshooting, they should not be an early adopter.

Seems like the vast majority of problems that people complain about on the forums are related to crapware they have acquired on their computers from previous installations and promiscuous downloading habits.

Arthur,

I've been in IT for 36 years so I've seen my share of people who have downloaded 'crapware' as you state. However, please spare me the 'Holier Than Thou' attitude.

This issue with the external disk drives is egregious and cannot be pinned onto the End User. Apple screwed up royally with this release as one should not be losing data from external drives. (Honest).

Interesting that you've singeld out Western Digital drives. This issue is happening with drives manufactured by Seagate, LaCie, et al.

It would therefore appear IMHO that the vast majority of problems that people complain about on the forums are related to not having their facts together before running off at the mouth.

I'd disconnect the seagate and boot into safe mode (hold shift down at restart) before you try installing.

I learned long ago, never to wrestle with a pig. You get dirty, and besides, the pig likes it.

George Bernard Shaw