One of the biggest effects caused by dropping hard drive prices and faster internet speeds is that we have more files on our computers. You may probably just randomly copied or downloaded tons of files to couple of default folders like "downloads". Then the question is how to sort them all? Digital Janitor presents an easy solution for this problem:

You select the folder you want to sort, then define the file types and the destination folder for these file types, and all there is left for you to do is clicking the “Auto-Sort” button, the program moves all the specified file types to your desired destination folder. Like all mp3 files to /music folder, all doc files to /documents folder and etc.

You can download the program from here

Renaming a couple of files is not a problem; select the file to be renamed click F2 and you are good to go, but when it comes renaming dozens of files, it becomes really burdensome. That's where comes RegToy FileRenamer for our help. It's a small but powerful program with lots of features.

RegToy FileRenamer is an advanced renamer tool for Windows. Some of its capabilities:

Batch file rename, full name, name without extension, rename just the extension, replace some characters, case renaming (all in lower case, upper case, random case, sentence case, tOOgLE case), substring (at beginning, at ending, at position; lenght), remove (at beginning, at ending, at position; lenght), reverse.

If you have multiple files needed renaming this is just the tool you need.
RegToy - Disk Cleaner
Batch file to replace file extensions
How to quickly replace the file extensions of several files

I have over 4000 mp3s on my hard disk. And I don't like burning mp3s to DVD with missing tags.
Most of my mp3s come from offline satellite download and they came named similar as below:
193.251.135.116_08C9A07485__66477.mp3
You have to rename them one by one according to their tags. This is the easy part since most of the media players can consolidate your library automatically.

* You can consolidate your music library with Windows Media Player by going to options and then enabling the rename and rearrange music using media information.

Main problem is with files without tags or with incorrect tags. This is where MusicBrainz Picard comes to rescue. By matching acoustic fingerprint of your files with its database, it correctly identifies and tags your mp3s. You can also set it to rename your files too in the process.
How to use it:
First adjust the program to your needs.
I enabled embedding cover images to tags and renaming file names.
Under 'View' enable 'File Browser'.
Select a folder which your files reside. Drag the folder under to the Unmatched Files in the center. You can drag the entire folder or choose files individually.

The tagger will read the metadata from each of the files and unless they have been tagged before, the files will be deposited into the "Unmatched files" folder. Files that have been tagged before and contain the MusicBrainz track identifier will be opened up as releases in the right-hand pane.
Once the tagger finishes processing the files, press the "Cluster" button (white square with 'clusters' on them). This will cause the tagger to attempt to group the files into album clusters by examining the metadata read from the files and clustering files that appear to belong to the same album. Files that are not matched into album clusters will remain in the "Unmatched files" folder. In future the tagger will automatically cluster the files when it has finished reading the metadata from the files.
If your existing files do not have an album tag, click on unmatched files to select all remaining files then click scan. All the matching tags will be shown on right pane. You only have to select the matching files and click save.
How to tags files with picard
Advanced tutorial
Musicbrainz server currently has info of 7138615 tracks.
You can also use album art plugin to add album arts in tags.
As an alternative you can also use Winamp for identifying your music files, it has a auto-tag feature which uses Gracenote database to find track information. You can access it by right clicking on any track / send to / auto tag.

Previously I have written how to change extensions of several files by using the command prompt in just a few steps. Now we will see another method for that purpose.

Suppose you want to change all files in a folder with bmp extensions to have them rar extensions instead.

Open Notepad and write:

ren *.bmp *.rar

save this file as renamer.bat

*.bmp is your default extension, *.rar is your preferred extension.
This bat file will rename all *.bmp extension files in the folder to *.rar extension files.

Sometimes it may be necessary to change the extensions of several files to allow compatibility with a particular program. For example you may need to change the extension of all the asp files in a folder to htm. If there are plenty of files in your folder it would be a very tedious work to do. But with a little command magic you can do the job in just a few steps.
For this example we will change all the files with an *.asp extension to a *.htm files.
If you want to keep the original files just in case use the below command at the CMD prompt or within a batch file:

xcopy *.asp *.htm

This would create a copy of all files with .asp extension and rename them to .htm, while keeping the original files.

If you simply wish to rename the extensions without keeping the original file you can just replace xcopy command to rename as below example.

rename *.asp *.htm

What if your files do not have any extension at all (there are programs that come in archives with text files that do not have extensons). For example if you want to add txt extension to all files in a folder open command prompt (win + R / cmd), navigate to your folder than enter the below command.

ren * *.jpg