I found this for you, a recipe and quite interesting
From: email@example.com (Gabi Shahar)
Subject: Dave's Horseradish
Selecting the root: Bring a small knife with you to the supermarket. Pick up every root you're considering buying and give it a squeeze. If it's limp, feels fleshy or flaccid, or wrinkled, forget it. Select only fresh roots that feel rather heavy for their size and are as hard as wood. Use the knife to pare off a thin bit of the root and pop it in your mouth. Bite down on it. If it makes your lip and tongue go numb and tingly, it's good. Don't buy it if it's weak, or if it leaves a bitter quinine aftertaste (the bitterness will be magnified by grinding.)
Preparation: Set up a table in front of a window. Open up the window and set up a fan to blow air OUT the window. Horseradish fumes are crippling and you will NOT be able to do this without pulling the fumes out the window. By exhausting air out rather than blowing in, you can even do this on a chilly night when you might otherwise not want a window open.
On the window table put your food processor. If you can run your processor with both the shredding blade in the top and the puree knives in the bottom, great. Set it up that way. If not, you'll have two steps (grating and pureeing) instead of one. Next to the processor, still in front of the window, put a large bowl. That's where the ground root will go. Close at hand (maybe on the kitchen table) put the jars where the root will be packed, a large bottle of vinegar, and your salt.
Step 1: Wash and peel. Put all the roots into the sink and start running a thin stream of cold water. Get them all wet and let them sit a few minutes to soften the dirt on them. With a stiff bristle brush, give them a good scrubbing under the stream of water. When they're clean, use a veggie peeler to pare off the brown skin and green tops (if they have green tops. You can cut the top inch off the root, leaving the greens alone, if you like, and plant them in your backyard if you want to grow your own.) Do the peeling under the running water, also. Keeping the water drizzling over the root while you peel carries off some of the volatile chemical, saving your life while you work in the sink.
Step 2: Grate and Grind. Bring the peeled roots over to the window table and turn the fan and your food processor on. Feed them down the chute to the grating wheel. The top wheel will grate the root, and the bottom knives will do the fine chopping (if you can't run both knives in your machine at once, you will have to grate each bowl full of root, then put the chopping knife in to finish separately.) As the root gets finer and finer, it will begin sticking to the sides and bottom of the bowl. Slowly, and with the processor still running, pour in vinegar to get a thick but not stick consistency. Continue to whirl in the bottom knives for several minutes, until the root bits are very very fine. Stop the processor and dump the processor bowl into the large bowl. Repeat these steps until all the roots are grated, ground, and in the large bowl. Remember to keep the fan on all this time! When all the roots have been processed, rinse the processor knives and bowl with cold running water. Wash them as necessary. Put the processor away or aside. You'll need the space on the table in front of the fan to pack the jars.
Step 3: Seasoning. You've still got that fan running, right? Leave the bowl in front of the fan. The grated root in the bowl should not be too dry. Stir in enough vinegar to give a smooth consistency. Taste a little bit of the puree (be careful! This is likely to be the strongest horseradish you've ever tasted.) If you think it needs salt, add some Kosher salt or canning salt. I usually add about half a teaspoon per quart.
Step 4: Packing. Use a ladle and a canning funnel to fill pint jars with the prepared horseradish. Fill the jars up, cap them off, and put them in the fridge. Do not process the jars. Keep them refrigerated. You may turn off the fan after all the jars are full and after all implements have been rinsed. The horseradish will maintain full potency for a couple of weeks (I make mine no more than a week or so before Easter) but will still be pretty damn strong for a month or two. Use it before it turns brown.
Cleaning up: Most of your tools (the bowls, ladle, etc) will require little more than a good rinse with cold water first (to neutralize and dilute any horseradish fumes) then hot water, since you aren't cutting any greasy fat.