Outlook Express problem -- software distribution service 2.0

My computer OS is XP. Recently, I have a lot of problems with my e-mail client Outlook Express 6.0. A few days ago, I found that when I clicked on the outlook express icon, Microsoft Outlook 2002 was launched instead telling my to set up my new profile. I have to restore to an earlier time to 'recover' my old settings. I have to restore to an earlier time everytime I switched on the computer to 'recover' my outlook express. I suspect it is this thing called 'software distribution service 2.0' that is causing the problem as when I switched off the computer, I noticed that the computer automatically installing updates. I checked the system recovery and discovered that the computer installed this thing call 'software distribution service 2.0 after I shutdown the computer'. Is this 'software distribution service 2.0' causing the problem or is there a virus on my computer? Thanks!