how to change folder for back up form C to another one?

I don't think that you can change it, I think it's fixed. Can you move some of the contents of your C drive to a different one so as to free up space ? Not everything on the iPad is backed up, so even if you've got 25 gig of content on the iPad, you may not need that much for the backup e.g. music in the iPod app, films/tv shows in the Videos apps, and photos synced from your computer aren't backed up, and nor are the apps themselves (just their content/settings),

This document list where the backups are stored: http://support.apple.com/kb/HT1766

I suspect there is a way to have Windows create a user's directory tree structure on a different device. Maybe create an account only for backups so you don't have to worry about the iTunes Store account or copying the iTunes library over. Just login and create the backup.

Reinstall to D: doesn't help the default locations.

I can suggest you to move the backup folder to D:, then create a Directory Junction by the mklink comand. How to do that, google will help you better than a single forum post 🙂

Step by step:

1. make sure iTunes is closed
2. open command prompt
3. CD "%APPDATA%\Apple Computer\MobileSync"
4. DIR
5. if you are in correct location, you will see listed the "Backup" directory there
6. open "My Computer" window, put in its location bar the path: %APPDATA%\Apple Computer\MobileSync (yep, without the "s) and press enter
7. you will see the Backup folder, MOVE (NOT copy, MOVE it!) it to your place of choose, in my example I will use the folder "D:\my test" to put backup in, but you have to use your own.
8. now you have the backup folder in "D:\my test\Backup"
9. go back to command prompt
10. DIR
11. now you see an empty directory (yep, we moved the backup dir)
12. now issue the command (be sure to use your correct directory of choose!):
13. MKLINK /J Backup "D:\my test\Backup"
14. DIR
15. you now see the Backup directory again
16. CD Backup
17. if all good, you will see the directories of your previous backups.
18. if not good, you just need move Backup folder back its own place, you havent lost nothing. But hardly the procedure fails 🙂
19. have fun!

It seems you using a windows version that still not support mklink, I guess Windows XP.

But not all lost, you can install (just unpack junction.exe and put it in a directory listed in your PATH) Junction from sysinternals, the command line will be:

junction Backup "D:\Jebote\Backup"

First time you run Junction, most likely an agreement window shows up, accept it.

instead of: MKLINK /J Backup "D:\my test\Backup"

you will have to write down: junction Backup "D:\Jebote\Backup"

"junction" will substitute the MKLINK command.

Sorry to have made you do extra steps, my bad thinking everyone using Vista+ systems. XP still around (and works good, too 😉 )

You first need to check if junction tool is working. Just type "junction" in command prompt and see if the usage help shows up. If happens "not recognized" as happens with mklink, it means the program is not in your path. If this the case, just copy junction.exe to c:\windows\system32 folder and retry the test.

Then, you have to be in the right directory to use the command:

C:

CD "%APPDATA%\Apple Computer\MobileSync"

junction Backup "D:\Jebote\Backup"

CD Backup

DIR

and now, it will lists the backups you done. Let me know.

you must not have a "backup" directory there, because you moved it. Did you copied only, instead?

Anyway, you now have junction working, so please follow these steps:

1. open command prompt
2. type these commands:
3. C:
4. CD "%APPDATA%\Apple Computer\MobileSync"
5. junction -d Backup
6. (note: it may return an error: its all ok, it means the Backup there is not a junction)
7. DIR

Please check the Backup directory not there. If is there, it means you haven't moved it but copied it. Don't worry. Check first if your "D:\Jebote\Backup" folder existing and with all data there. If OK, go folder %APPDATA%\Apple Computer\MobileSync and delete the Backup folder.

Then, type these commands in your command prompt:

1. C:
2. CD "%APPDATA%\Apple Computer\MobileSync"
3. DIR
4. check DIR result and make sure there is not the Backup directory
5. JUNCTION Backup "D:\Jebote\Backup"
6. now a junction has been made, to check it:
7. CD Backup
8. DIR
9. if all ok, the dir command lists the Backup content
10. done!. Hopefully.