Back up to 4G USB

I'm trying to backup to 4G USB using AA1 but it stops saying not enough space the dta on the Acer is only 3.5 G

 

Sloved as follows

In most cases a smaller USB drive will also work due to the data being compressed during the backup. Not already compressed data is compressed by a factor of 2:1 on average at a speed of about 40 MB/s, which exceeds the write speed of any USB stick and most portable external hard drives. Free space is compressed by a factor of 250:1. Note that most of the free space may not be really empty, depending on the amount of data already written to the drive, but just not indexed in the file table. To get the increased compression ratio just overwrite all free space with zeros. There are probably a few freeware tools to do this in Windows, one of them is eraser. In Linux only a single command is required.
dd if=/dev/zero of=zero; rm -f zero

from http://www.kuki.me/2009/03/how-to-acer- ... hd-backup/

 

Looks like you're doing a whole-partition backup. You might want to look into fsarchiver - similar to gparted (and, probably, whatever you're using if it's not gparted) but doesn't save the empty space. Eliminates the need to use dd.