ok i followed some info from this page to add sort by size functionality to mac os x’s find / search funtion, so all credit to their respective authors as mentioned on the above page, what i have attempted to do on this post is to add the extra information to make the procedure foolproof from my experiencing of doing it. if you follow this information i will not in any way be held responsible if you naff this procedure up.

1: open a new finder window in list mode
2: go to the view menu and select “Show view options”
3: tick an unticked custom column to be shown “version will do”
4: close the window, the reason we did this was to guaranteably create if it wasnt already created a com.apple.finder.plist preference file in your currently logged in users folder ie ~/library/preferences/ folder as by default that file may not necessarily exist, which was the case in my case.

5: now we will follow the guide as shown on the page linked above, which i will quote wholesale from the mac os x hints post itself below rather than crazily re-write quality instructions many thanks to vl_tone
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“I was very disappointed that I couldn’t add the Size column to the list view in search results in Snow Leopard like you could do in Tiger, since Apple gave us the impression that Spotlight would include additional ways to sort results in Snow Leopard. Only Date Created and Date Modified were added as options in 10.6; the others are grayed out.

Fortunately, I found a way to force the Size column to appear, as well as Comments, Version and Label columns. You’ll have to edit the com.apple.finder.plist file found in ~/Library/Preferences, using the Property List Editor app (included with Xcode) or PlistEdit Pro.

Open the Root node, then navigate down into SearchViewSettings » ListViewSettings » columns. Then choose the column you want to activate in the column list (ie. Size), and set the visible key to yes. Save the .plist and relaunch the Finder (Option-Control-click on the Finder icon in the Dock).

Note: you must have done at least one search, and selected one of the additional columns in the View Options panel for the search results (Date Created, for example), or else your .plist file may not contain the SearchViewSettings node.

Warning: Apple probably disabled these columns for a good reason, as there may be some bugs that could cause problems on your system. I didn’t have any problems with the size column, but be warned.

[robg adds: I have no idea why it’s taken over three years (and counting) to fix something that worked in 10.4. Until Apple gets it fixed, though, this seems to do the trick. I tested it on my MacBook Pro, and haven’t had any problems as of yet. Note that you won’t be able to actively enable/disable the columns in the View Options dialog, but all the columns you set to yes will show in your search results — and once they’re showing, you can sort as expected by simply clicking a column heading.]”
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once you have done this it should have done the trick if not follow point 6 :

6: ok once you have done this, the sort by size column should already now be visible, if the by size column is not yet visible in search then as overkill, run the script below also taken wholesale from the same post, credit for this goes to the brain power of tedw as this also modifies the value for size in the same plist file and restarts the finder to boot to guarantee the change is visible without restarting the computer. you in fact could probably get away with skipping step 5 completely and just running this script from step 6, but I did all these steps and it worked for me first time, steps 1-4 for me were as essential as initially the the plist file itself didnt exist in that location, and where it did exist it didnt contain the right modifiable property values.
tedw wrote > ——————-
“Just to help people out, here’s a script that adds the size column to Finder searches.

tell application "Finder" to quit
tell application "System Events"
	set theFinderPrefsFile to POSIX path of (file "com.apple.finder.plist" of preferences folder of user domain)
	set theFinderPlist to property list file theFinderPrefsFile
	tell theFinderPlist
		tell property list item "SearchViewSettings"
			tell property list item "ListViewSettings"
				tell property list item "columns"
					tell property list item "size"
						set value of property list item "visible" to true
					end tell
				end tell
			end tell
		end tell
	end tell
end tell
delay 3 -- just to make sure the plist file is written to disk
tell application "Finder" to launch

To remove the size search, set visible to false instead of true in the above. My concern with this is that it would force the system to calculate file sizes at search time, which might slow down searches some and increase processor activity. Has anyone noticed that kind of effect? P.s – to use this, open the Applescript Editor in the Utilities folder, copy this script into it, and click Run.”
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postscript :

Now obviously all this gubbins above may seem a dire endightment of an now largely abandoned operating system from a bug fix perspective, but sadly if you want sort by size functionality on searches in snow leopard it is the only way. and thanks to macosxhints website for providing the forum for users to resolve such stuff amongst themselves.