Advanced Disk Catalog - Basic and fast for knowing what i have in any cd/dvd
FSResizer - For batch editing pics. I used it for changing the colors of the buttons for skinning with very good results
SuperFlexible synchronizer - synchronization between differente disk, ftp, web, etc
Autohotkey - Scripting, macros, hotkeys manager, really useful software, highly recommended.
Spek - Spectrogram for local files
Spectrogram 16 from visualization software - Spectrogram for what you are listening in the speakers. Know the quality of music before downloading.
14arenamer - A really good oldie for renaming files
Tag&Rename - Advanced tagging of mp3 files. Together with 14arenamer i use it to rename the files.
F.Lux - For decreasing color temperature at night
Notepad++ - A very good text editor
Sandboxie - A sandbox for testing software
XnView - For browsing pics, is the one i can configure nearer to the classic ACDSee 3.1. The zoom interpolation can be disabled for watching real pixels instead of added ones. Lightweight and fast to start disabling unneeded plugins
BWmeter - Check the network usage, shows different alerts, very useful for 3G connections
Proxomitron - Freedom...
Synthesia - Learn playing piano with any midi file
Emu48 - For my beloved calculators Hp48 and Hp49
Microsoft Mathematics - Very helpful for trigonometrics and graphical drawings
Native Instruments Traktor 2 - Mix your favourite songs
Mixmeister BPM analyzer - Add the BPM count to your files, is not very precise. Sometimes it doubles the real BPM. Very helpful for mixing songs or creating smartplaylist with different purposes
Speedfan - Reduce the noise of your fans while watching the temps
Tthrotle - Reduce the speed of your cpu to keep the temperature to some level
Firefox addons: about:addons-memory, brief, Cookie whitlist-with buttons, flash video downloader, imglikeopera, leechblock, memory restart, pop video, rss icon for brief, toggle word wrap, undo close replacement, click to play switch, sun cult
@Iasc: As far as i know xmlc files are not editable. They are compiled skins created using Skincreator from Steven. Would be nice having that possibility...