I was having the following problems with my laptop for the past 1+ year : Every time I logged into an account on my Windows XP MC pc, lsass.exe would take up 100% of the cpu for a good 3 to 5 minutes and then return to normal. This made my logging into Windows take forever (as you can imagine). I googled around and posted in this forum and I always got the same answer : it's probably malware. I scanned with everything and it's mother (SAS, Malware Bytes, KAS, AVG, Avast, Dr. Web) and yet no malware was ever found. Some of the more exotic answers I got were things like : delete my prefetch (maybe it was corrupt), transfer my user information to a new user account then delete the old one (maybe it was corrupt), etc.. None worked. I was so fed up I decided to just go ahead and reformat. Yesterday before I went through with the reformat, I decided to google around one last time. This is what I found : http://forums.prophecy.co.za/f10/lsass-exe-windows-encryption-22567/ I won't even pretend to say I understand what's going on there but the poster recommended finding and deleting the following directory : C:\Documents and Settings\problemuser\Application Data\Microsoft\Protect (where "problemuser" is the name of the user account having the lsass.exe issues, for me it was both my admin and user account). I usually wouldn't delete a directory without understanding what it does but since I was going to reformat anyway, I decided what the heck, let me do it. I deleted the directory in both my accounts and restarted the pc. Care to guess what happened? The lsass.exe problem was GONE! I just wanted to share this solution with members on this forum who may have been having a similar problem. I never seen this solution suggested either.