The Phrase "K-Rad", first created in the early 1980s, has continued to find common use among the computer-savvy youth of today, even though its original history and age have been obscured.
Additional Notes:  
The phrase "K-Rad" was used quite a lot during the 1980's on BBSes. By the time of the third wave BBSes (1989-1996), it was already a term used in parody, to indicate someone clueless or a general loser online. Two theories of the etymology are in conflict:

"K" is short for "Thousand", as in Kilobyte, and therefore "K-Rad" means "A Thousand Times As Rad".

"K" is short for "OK", as in "OK, Rad."

Which is it?

I can't resist but include two other possibilites, sent to my by one Sam Brown:

"The Term Krad derived from KMART - See G-philes pertaining to K-mart (during the early 80's) Kwalitee." also, the user "Dark Knight" have coined such a term, Krad being DARK spelled backwards, and we all knew how l33t it was to spell your shit backwards (REVO EMAG) etc."

I'm not inclined to go with that, but I had to include them.

The United Phone Losers discuss their own parody "F-Rad", and in doing so, come up with yet another theory on the history of K-Rad: "As most everyone knows, back in the day, neato-leeto hackers used to think it was really cool to use a "k" prefix before words like Rad and Kool. So often times you'd see the words k-rad and k-kool and a what not. If you do that now-a-days, however, most people just laugh at you and poke at you with sticks. Even I will make fun of you for doing it. But anyway, the k standed for killer or something.... like: "hey, that's killer-rad(k-rad)!". Then one day in #phonelosers while i was talking to nawleed, we thought we should make our own neato-leeto prefix to be mocked for. So we decided to make it the trusty letter "f"!! So now you can often visit #phonelosers and see losers like me and n0llid saying stuff like "hey, that crazy website was f-rad!". "hmmmmm, this new cell-fone is f-kool!" etc."

Jonathan Armstrong has given me a file from The Incognito of The Curse BBS, in which the following paragraph appears:

"I recall when Hot Rod, Darc Deathe and The Warezird was over at my house and we had a new ware called "How About a Nice Game of Chess?". After Rod cracked it, which didn't take very long, we put a title page on it. Now, most pirates had "Call these RAD boards..etc" on their title pages but I wanted something different. At the time Apple Bandit used "Kbye" when he finished chating or talking with people. So I came up with "K-Kool". And we put on the title page "Call These K-Kool boards..etc". In fact Dave (Darc Deathe) stated "Watch how fast people start using that word". And amazingly people did. Too many people started to use the word that it got downgraded. It used to be a hip thing to say. I remember when Rabid Rasta put out his humorous text file called "The Real Pirate's Guide" in which he said "Real Pirates Don't Care About The Curse's K-Kool mods". It seems the creation of new and original mods might be getting out of hand (overkill). But, everyone seemed to enjoy it and The Curse prospered because of it. Plus, I had way too much fun creating/making them to stop."

If this is accurate, then this is the source of K-Rad.

krad.txt (562) Citations and Timestamps for Various K-Rad Influences
vgirl.txt (4.4K) Lyrics to "Valley Girl", by Frank Zappa, May, 1982.
k-rad.html (6.3K) Strongly written report on the origins of K-Rad, by Formica.
dornquast.txt (2.3K) The Meaning of K-Rad, posted by Matthew Dornquast (Mini-Appler) in news.newusers.questions and alt.2600 (November 15, 1994)
cursehist.txt (16K) The History of the Curse BBS by the Incognito
miniappler.txt (1.1K) The Meaning of "K" by Mini Appler
k-analysis (301) Citations I have Stumbled Across in Printouts WAREZ Magazine: Example of Post-1990 revivial of "K-" prefix The Yak's Frequently Question Answer on the Origin of K-Rad (Thousand) K-Rad BMX Tires! (Sorry, had to throw this in.) Incredibly, the Netscape UK "Emoticons" page describes the K- prefix as "Extremely-".