Right, I'll start at the beginning....I updated my MacBook Air to Mavericks.... no problem, even let it run a week before taking the plunge to install it over Mountain Lion on my 2007 iMAC. NOW there IS a problem! As my iMAC has different users, each have their own login ID. 35mins to swap users....not a happy bunny, so I complained on the forum that perhaps Mavericks had not been fully tested and had mushed up my iMAC as it was an older version....hey presto....'try installing the update' came the reply (I thought the system was supposed to offer those automatically?)....OK....installed it, still no change and now I noticed that the printer also was not available but that was probably the case before. After much swearing I decided to go back to OS X ML. NO CAN DO as the App Store - although showing it in 'My Purchases' - wouldn't let me download it as it was no longer available....hence my annoyance at Apple.... this is MY Area for storing MY Purchases and as such should let me download whenever I want.
So, annoyed, I decided to wipe the hard drive and start over again with OS X Tiger (the discs supplied with my original purchased iMAC). This is where I learned that on start-up, grey screen, press 'cmd-R' to access the OS X Utilities AND Wi-Fi. So to cut a very long story short I have now got as far as risking the reinstallation of Mavericks, and have managed to reinstall from the App Store all my previous Apps (they don't download so that you can back them up, only install directly)
Trying to print wirelessly to my Epson SX425W brought up a 'pop-up' and automatically installed the relevant software through my wireless connection and all seems to be sublime again, and I am once again a happy MACite!
MORAL OF THE STORY:-
1. MAC's are sooooo much better than PC's, easier to put right (although the way I did it was lengthy process!) and...
2. .....before updating to a new OS - BACK EVERYTHING UP! something I had learned through a bad expence some years ago with a PC - but had unfortunately I had forgotten this! This will save time and perhaps 'uwarranted' rantings directed at Apple.