How do I change my primary PC synced with my iPhone

Welcome to the discussions,
Back up your iTunes and restore it on your new PC: http://support.apple.com/kb/HT1382
Make sure your new computer is authorized in iTunes. Disable autosync in itunes, connect your iphone, right click on it in the device list and choose backup.
This will save data, pictures and settings to itunes. See what's included in this backup here: http://support.apple.com/kb/HT1766
Transfer your purchases the same way to copy all apps and bought media from the Store to your computer.
Set up at least one contact and event on your computer to be able the merge your calendars and contacts after your iphone got wiped during the first sync.
The rest of the data can be restored from the backup you made.
Restoring: http://support.apple.com/kb/HT1414
Music is one way only, from the computer to your device, unless you bought the songs in itunes and transferred your purchases.
There is 3rd party software out there, but not supported by Apple, see this thread: http://discussions.apple.com/thread.jspa?threadID=2013615&tstart=0

Message was edited by: Ingo2711

If you mean photos in the photo app you must copy the photos to your home PC from your office PC via a backup process, as with music. There is no way to copy photos in the photo app from the iPhone to your PC, except with some 3rd party programs that you can find with Google. Note that even if you do this the resolution will be lower than the originals because photos on the iPhone are reduced in size and optimized for the phone.

If you mean photos in your camera roll you can sync them to the home computer using the Windows camera and scanner wizard.

Did you try to create a new folder and copy the pictures into that one and point itunes to this new folder?
Did you check the read/write properties of the folders?

Just one more thing: Did you try to delete the ipod photo cache folder and sync again?: http://support.apple.com/kb/TS1314