That is a permission error, it appears that the saved export data is not read-writable on the new computer.
You will need to fix the access permissions before calibre can touch those files. Just right-click, access the properties, and fix the security settings. Or something like that, I haven't used Windows in a while so I don't really remember exactly where those settings are found.
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This sometimes happens, especially with people who are not huge computer geeks.
Probably because the flashdrive or external hard drive you used is NTFS instead of FAT32?
As a general rule of thumb, those permission errors can trip you up for any data you transfer from computer to computer. One of the reasons to prefer FAT32 for transferrable data. But hardware vendors have a pernicious habit of shipping such devices as NTFS.
