Having problems backing up to a usb stick. 64GB with half free. Have backed up in the past on it and it still has those files on it in a folder. last few times ive tried to back up its gone through the process taken around an hour to do but when i go into the drive they aren't there. Dont get any error messages whilst its copying over. Any clues please,

Are the file sizes over 4GB?

Your USB stick my be formated as fat32 which has a file size limit of pretty much 4GB I can't remember if Windows would warn you of this or not.

If it's being copied over from backup software that could be a reason your not getting any errors as Windows isn't handling the backup.

If this is the case an easy fix maybe to format the USB stick as ntfs this format can support +4GB files and above.

Let us know how you get on.

+1 to Mark's suggestion.

However if you bought the stick on ebay (or a market etc) it could well be a hookey one, they reprogram smaller ones to appear to be bigger than they are. Usually as long as you stay under the actual size all appears normal but if you go above that size things start going wrong and disappear etc.

What actually happens depends how its been programmed, sometimes they lose old files, sometimes they lose new. Sometimes the files appear to be there in the directory listing and even have the right size recorded but that's only the index and the actual file no longer exists or is duplicate of other data on the drive. Sometimes you just get weird errors once its filled up to a certain level.

Annoyingly the bigger drives get, the longer it takes to test them and the less likely people find out they are wrong/faulty.

I've had loads of ebay refunds on them, the seller is usually deleted either before or after I have reported them. I did feel sorry one time as the seller had been making pin-money on ebay for a long time but had accidentally bought a stock of dodgy ones in all innocence which left them well out of pocket.

In addition to Diggingdeeper's reply, a quick search online will reveal a USB drive checker that will show the true capacity of the USB drive. Sorry I can't remember the name of it.

Best not to use them as backup as they are very sensitive to changes of temp from one computer to another. Fine for transporting files from one place to another but not long term storage. DVDs much better option.

Think i got it from a reputable source and when i check its properties it does say 64gb with so many used and so many free. Whats freaked me a bit is that i went to clear out my internet History and there were several thousand items to delete the number matched within about 50 the number of files i was trying to back up. Just coincidence? I dont usually have thousands of History items to delete.
Will try and back up a few files onto the USB in smaller batches rather than trying to do the entire 3gb in one go.

Due to the quirky way Windows copies files and can easily get "stuck" with one file and ruin the whole copy, you might be better writing a little script using the excellent and free ROBOCOPY program.

https://social.technet.microsoft.com/wiki/contents/articles/1073.robocopy-and-a-few-examples.aspx

You could also set up a scheduled task weekly to do the backup.