tested the ISOs you're downloading VerifyIsoHowto https://help.ubuntu.com/community/VerifyIsoHowto used gpg to check the MD5SUM file's cryptographic signature How-to: Verify ISO (Ubuntu Community Documentation) http://help.ubuntu.com/community/VerifyIsoHowto https://help.ubuntu.com/community/VerifyIsoHowto https://help.ubuntu.com/community/VerifyIsoHowto VerifyIsoHowto http://help.ubuntu.com/community/VerifyIsoHowto help.ubuntu.com/community/VerifyIsoHowto VerifyIsoHowto How-to: Verify ISO (Ubuntu Community Documentation) http://help.ubuntu.com/community/VerifyIsoHowto How-to: Verify ISO (Ubuntu Community Documentation) check the integrity howto