If you are unable to copy Outlook PST files then it is confirm that your PST files have been over-sized and corrupt. So, you need to split Outlook PST files in order to resolve the issue. You can divide large sized files with the help of third-party PST Splitter Tool.
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Just download Long Path Tool to avoid errors while copying.
If you are unable to copy Outlook PST files then it is confirm that your PST files have been over-sized and corrupt. So, you need to split Outlook PST files in order to resolve the issue. You can divide large sized files with the help of third-party PST Splitter Tool.
It looks like your external hard disk in FAT32 system and outlook messages file .PST is more then 4GB.
To know the file system of the Hard Disk right click on the drive select properties.
Check your file system first. FAT32 will not support more than file size of 4GB.
There are 2 options to copy.
1. Split the .PST in to 2 or more outlook data file
or
2. Convert the FAT32 System to NTFS.
To convert from FAT32 to NTFS. go to following link
http://support.microsoft.com/kb/307881