Can’t modify folder with domain admin username

I have two servers on a particular domain.
1 is running 2003 r2 standard and the other is running 2008 enterprise.
I recently switched to Acronis Backup and Recovery with a RDX usb 360gb drive because of a hardware failure.
My problem is I need to get files from the win2003 server to the win2008 server. I created a shared drive, gave the domain admin full permissions yet everytime I try to create, modify, or delete a file on the shared drive I get an access denied error.
I researched as best I could and everyone says disable UAC but I’ve all ready done that and it still doesn’t work.
I appreciate any help to what is probably an idiot question and apologize if the answer is already posted. I couldn’t find anything that helped.