Here is the system I devised after a few years of collecting. I only wish I had started SOME sort of organizing when I was only a few months into it.
I have a REALLY big folder on my Puter called SCRAP. It contains `DOWNLOADS, which is divided by month, then site. There is also a main folder called `PREVIEWS. Those start with an accent, which keeps them at the top of the folder. There are also folders for Alphas, Kits, Mega Kits, Commercial use, QPs &BBs as well as MONTH_ToBURN
When I get a chance to organize them, I unzip the kit, and put it all into one folder (most designers split a kit into multiple zips so they are easier to DL) I delete extra copies of previews etc. I rename any files to DesignerName_Kit_Piece, and curse any designer who makes me do this step. I think it should be an industry standard. I name that folder DESIGNERNAME_KIT_SITE. I then move it to my Kits folder I make a copy of the preview, named DESIGNERNAME_KIT_SITE_DATE, and they all go into `PREVIEWS, so if I am looking for something, I have a chance of finding it.
I make a new zip of the whole kit, which I put into a monthly file, to burn to DVD. As soon as there is enough in there, I burn the disk for backup, and copy it to my external drive. I check them for errors, then delete that Burn file.
Mega Kits are done in one big folder, usually named SITE_DATE_THEME. I keep each designers stuff in a separate sub-folder, I usually make one patchwork preview for the Mega kit, rather than a bunch of little ones. I zip the whole Mega together for the burn disk.
If the alpha is not too specific to a kit theme, I put a copy in the Alpha folder, and make it a separate preview (in a sub-folder).
After the kit is all cleaned up and zipped, and the zip is checked for errors, I delete the original downloads. When my hard drive gets too full, I can delete some of the kit and mega kit folders that are out of season, or not my current favorites. The preview stays in the folder, and it tells me what disk the kit is zipped on. Alphas are usually generic, so I donít delete them even if the kit goes.
As well as cleaning up the current kits, I am slowly working my way through a few years of older kits, but it will take quite a while to catch up.