On turning on my computer, I get error messages. I tried going to Microsoft.com to get download for Windows 2000 installer, but in clicking the button, it does nothing. With this problem in place I purchased Norton Antivirus 2005, but am unable to install this. The error msgs I receive are: 0xc0000142 and 0x77e8801e. I believe all this started when i "upgraded" Yahoo. Now I can't get Yahoo to work properly (respond to msgs, delete msgs, etc.) Yahoo is of no help, and apparently I somehow replaced Windows files with unrecognized files. A BIG, BIG mess, and I need h e l p!!!