How do I change my bidding profile to PRIVATE as seen by other bidders.

[kroutpick]

Actually, no one sees what you have purchased nor your bidding history on a specific item, you are the only one who can see it.

The "private" feature was to protect that thing before that eBay has changed their privacy policy.

IMHO, this doesn't change anything now.

If you are talking about the visibility of your feedback history, look here :

http://feedback.ebay.ca/ws/eBayISAPI.dll?FeedbackOption2

Note that :

If you make your Feedback Profile private, your Feedback comments will be hidden from other users. This may decrease the chance that other members will want to do business with you.

People may ask themselves : what do you have to hide?

[reallynicestamps]

If you don't want those who have access to your computer to know what you are buying, and frankly no one else cares, change your username and don't tell it to anyone, change your password and don't tell it to anyone, and log out from eBay when you leave the site.