Question : Problem: Copying files to external hard drive

I've bought an external hard drive (Western Digital My Book) for my laptop (HP Pavilion DV 4000).  I am wanting to save my photos and video files to the hard drive.  I've done this by dragging and dropping the files from the laptop to the external hard drive.  I'm using Windows 2000 XP (I think)

To check that all files were copied I right clicked on the folder to see how many files were in there.  I learnt that I had the same number of files but when I checked the folder size it was different.  
eg. Copied folder: Size: 4.30MB Size on disk: 4.34MB
Original folder: Size 4.30MB Size on disk: 4.34MB

Have I done something wrong?  Why has it changed?  Why is the file size different to the size on disk.  Does this mean the files will be corrupted more easily now?

I was copying one folder over and it said that I had a cyclic error.  I found I couldn't play the file so I assume the file was corrupted some how.  Does cyclic error mean anything in particular?

Answer : Problem: Copying files to external hard drive

Windows can sometimes have a different "opinion" of the size of files, so you may see it different.

As for the CRC errors, usually that's due to a disruption of the copy process of soem sort, or bad areas on the disk. All hard drives can potentially have bad areas on their disk.
You may want to go to the command prompt in windows .... start - run - cmd
then type  chkdsk /r for your main drive
or if you external is drive x, for instance, you can type
chkdsk x: /r
This might help fix any disk errors before you copy data to it.
Hope that helps.