I don't have a lot of free memory in my computer so I wanted to hold my backups on my flash drive of 1tb. However, neighborhood backups can't be fully copied. I get thise errors where I can either try again, skip or cancel and half of the files can't be copied. I restarted my computer so nothing is running in the background. I have no problems copying these files generally. What is the issue here?

What exactly is the error message that you get? Could you tell me what the text actually says please?

That error indicates that the source is not valid. I would guess that the name you've given to your folder may have something to do with it- try renaming the folder to N005_12_9_24 instead of using the full stops.

Maybe the hard drive is failing. Right-click on the disk drive, bring up properties and have it checked for errors. If there are any, you may need help from an expert to prevent further data loss.

Other things to try @moonlight__ is to make sure the game, simPE, the Clean Installer, etc. aren't running while you are trying to copy files. Nothing else should be trying to access the files while you are copying/moving files. Basic I know, but just in case. Next, try zipping the folder first--it doesn't have to be a zip exactly; you can make it a rar or whatever the extension for 7 zip uses (.7z ?). But I find folders like neighborhoods and downloads can be really big so it can be helpful to package them first, then move them between hard drives or SSD drives. It helps with preventing errors during copying and moving, plus makes it a little easier to move because the file is smaller.

Thanks guys, I'll try what you recommended to me. I don't know if this is valid info but I have around 1-2GB free on my drive and I don't run anything in the background while copying. I'll try the renaming method as soon as I can

It's possible the 1-2 free GB is used on and off by various processes on the computer while it's coping, and causing errors because of access issues. 1-2 GB is very little harddrive to run a computer with. There are background tasks running even if you're not doing anything on the computer.

Do you have the option to move some other files (not used by the game or anything else important on your computer) to the flash drive? It would be better to have at least 10 GB free harddrive (preferably a lot more) for the computer and the game to run alright and save files properly. My old laptop started complaining every time I got below 10 GB and tried saving larger files or run heavy programs.

If you've got a selection of backups, you can keep the latest and move the older ones to the flash drive. If you move the files instead of copying them, you'll more easily know which files are causing trouble (they'll be left in their respective folders).