I am experiencing issues installing a new copy of a three PC ESET Smart Sec 5. The three machines all use differing operating systems; XP Pro, Vista and Seven. The software doesn't want to install on any of them. With the XP machine, the installation seems to work, but the computer then becomes extremely slow. With the Vista machine, the software will not even install. Instead I am informed that the Windows Installer does not work. I have not had any difficulty installing other software. And with the Seven machine, I get the error code 2878. I had tried to look this up on ESET's website, but I have had no success. Given the fact that this software is failing to install on all three computers, I am wondering if I just have a bad disk. Any thoughts on this matter? I have used ESET in the past and have never had any difficulty before. Thank the forum in advance. Regards, The Tree.