I posted this question on the Kaspersky forums as well, but given the question is generic, I'm hoping the experts here can chime in as well!! I recently uninstalled Norton 360 due to issues with ccApp taking upwards of a GB of RAM on the PC when playing online games. Tech Support was practically useless (I stopped trying when they started going over the re-install procedures). So, as I have a license for KIS, I decided to give it a try on Vista - While its "Vista Compatible", I don't think it has Microsoft's certification yet, which is why I switched. After uninstalling Norton 360 using the Norton Uninstall Utility and rebooting, I tried installing KIS 6 (621 release) several times. Following the screens (install location, Complete install, etc.), I would get to the installation part itself where two pop-up errors would appear that simply contained "Installation failed."). The funny part is, clicking OK on these windows would allow KIS to continue through. After reboot, KIS appears to be functioning normally - getting updates, scanning, all services working, etc. - But two things concern me: First, the errors themselves (i.e. is something on my computer blocking KIS' install), and second the hour my PC didnt have security software. I did a little research on my PC, and I'm showing Norton 360 in the "installed AV" and "installed firewall" listings of Security Center. I have instructions on removing several registry entries that may be sitting out there still. Granted, I'm behind a NAT firewall router, Vista is fully patched, KIS' full scan detected nothing, and during the time w/o software I wrote to you on a different PC (so I wasn't surfing the web unprotected). These may be anal-retentive questions (particularly since I'm very safe with surfing, have no real 3rd party / shareware / etc apps installed, etc.), but thought it worth seeing if anyone else would be concerned. Thanks in advance!