WinDiff

[URL]
Google: windiff
or just copy from xp disc, \support\tools\support.cab, copy 3 files: windiff.exe, windiff.hlp(optional), gutils.dll

[Hardware Platform]
X86

[Software Platform (OS)]
WXP+SP2

[Need Installation?]
NO

[Version Recommended]
from xp disc

WinMerge

[URL]
Google: winmerge

[Hardware Platform]
X86

[Software Platform (OS)]
WXP+SP2

[Language]
Unicode

[Need Installation?]
NO

[Software Files]
(you can see Files.txt)
Filters/
MergePlugins/
Language/
Docs/
Register.bat
UnRegister.bat
WinMergeU.exe (except for Windows 98/ME users who should use WinMerge.exe).
...

[RunTime]
Register.bat
UnRegister.bat
also see:
http://winmerge.org/2.6/manual/Installing.html
(5.4 Shell Integration）

[Portable Support]
official: .zip
portableapps: also offer(try?)

(There are 7-Zip MSI installers that do not install all the files WinMerge needs (namely 7zip_pad.xml in 7-Zip program folder). If there are problems with archive support enabling, try running the EXE version of the 7-Zip installer.)
WinMerge can support packed archives only if 7-zip plugins exists. you can in options->pack support, click the url...
or in help->check archive support... click url...(note: if Merge7z***U.dll is copied the same dir as winmergeru.dll, this menu item disappears)
also see "5.5.7-Zip and Archive Support" in http://winmerge.org/2.6/manual/Installing.html
my experience:
Shared intallation: copy Merge7z***[U].dll (depend on the file(s)) you selected to system32
Application specificl installation: copy to the path where the .exe file you specify reside. under this installation, check "Enable standalone operation" to copy only lang/ 7zip_pad.xml , 7z.dll and the latest Merge7z***.dll and Merge7z***U.dll.

AptDiff

[?]
by the author of aptedit, but freeware

[URL]
Google: aptdiff

[Hardware Platform]
X86

[Software Platform (OS)]
WXP+SP2

[Need Installation?]
YES

[Can be Greened?]
YES

[Howto Update/Upgrade]
adupdate.exe (it will slowly downlaod the latest adsetup.exe - when process is 100%, click "minimize to tray" and the setup dialog pop up)

[Software Files]
see unins000.dat (unins000.exe calls it)

[RunTime]
also see unins000.dat, it has info about reg operation for context menu

[Portable Support]
Officail: only .exe.
also no result in internet for portableapps.
tc-ctrlpagedown:no.
7-zip:no.
UE:guessed right, but failed
PEiD: Borland Delphi 2.0 [Overlay]
but it offered an uninstall log file which says:
Inno Setup Uninstall Log
and a list of files and reg operations

File Comparision

you can:

in Total Commander, choose any 2 files, then such menu item will appear in:
ZoneAlarm's Main Menu->Files->Compare By Content...