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I don't believe that Lenovo is still offering X41T restore disks. Your best bet may be to post a WTB (Want To Buy) in the Marketplace.
In researching online how to get the best performance from the X41 Tablet, I've come across references to the factory restore image being part of the problem. In an article entitled "How to speed up your Lenovo X41T", the author talks of original IBM X41 utilities and bloatware that, when installed as part of the recovery process, have a profoundly negative affect on system performance.
My thinking here is that maybe installing the original factory image isn't the best way to go.
What do you think of using an OEM XP Pro SP2 disk (with the XP Tablet PC COA key that came with the tablet) and select driver/utility downloads from the Lenovo site as a better approach for installing the XP OS in 2011?