I've tried two decompressors: ADL and Universal, and they both say the Ubuntu 11.10-desktop.iso is corrupt.
I'd like to bypass this step and install on my 4Gb flash drive.
You do not have to decompress the .ISO file to install it on a USB drive. Go to this web site and download the USB pendrive installer USB installer
You did not say if you were using Windows or not. This little guy should do the trick.