In Microsoft's ongoing efforts to unseat AOL as the 300-pound gorilla of online service providers, its MSN Internet Access division is rolling out an AOL defection tool this Tuesday.

With MSN's Switching Tool, the firm says it takes three steps to migrate an AOL customer's address book, calendar and archived email over to MSN. As part of the deal, Microsoft will cancel a user's AOL account and for 30 days will forward to their new address any email sent to your AOL address.

MSN began its campaign to woo AOL users a year ago by introducing MSN Explorer, a simple browser with hooks to the MSN portal, along with a big marketing campaign.

Since then, just under two million AOL members have defected to MSN Internet Access, MSN representatives claim.

AOL users are the least likely to change ISPs, partly because AOL doesn't make it easy to switch. The irony is easy to see — MSN's cancellation process isn't getting easier, while it makes AOL's process 'hassle free'. Up to now ISPs have shared the secret that none of them wants to make it easy to cancel a service.

As the number two ISP, MSN shows signs of gaining on AOL. MSN says its membership has doubled over the past year to eight million. Meanwhile AOL reports a membership of 34 million, with new customers signing on at a slowing pace.

Both MSN and AOL have paid dearly for market share in their bitter war for the loyalty of average online consumers.