That is really good question, and I think there is a way to sign out of icloud control panel and sign in another, but lets look at what is that going to give you.
1. Photostream album is in default and same location and you eventually going to merge photos from both accounts.
2. Outlook is going to sync with the same profile, so you are going to merge account contacts and calendars as well.
3. So while the ability physically there, to use different accounts on same PC account, the consequences are something that you really want to avoid.
4 Seeing how disinclined you are to create another PC user let me Google instructions for you.
Now if you are ok to have photos downloaded and do not use contacts or calendars sync that signing out and in will actually work for you.
So by all means go to control panel- icloud- sign out- sign in and give you computer time to see the results of that. I can not predict the results,
for the reason the photostream is not syncing pictures backwards, but rather streams currently taken pictures starting with the moment of the sign
in and installing and turning on icloud. On another hand it backs up those pictures for 30 days, to allow download to all signed in devices. So without
someone actually trying that I hesitate to predict result.