OK,
I have read EXTENSIVELY on the whole upgrade, new install, migrate databases, export tables yadda, yadda, yadda...

the bottom line is this: some modules on the "old site" (1.39H) no longer work, as they were done "privately" by a freelancer, who no longer exists. these modifications are site wide, embedded & difficult to track down & remove. So I do not / cannot "Just Up-Grade"

I am fairly competent. I have installed 1.51, and a template (a fairly complex on at that) so far so good. I had thought that using easy populate (on 1.39h) & installing easy populate on the 1.51 site, I should be able to export product lists & later customer lists as well. I do not have a huge number of products but they are interlinked, (some of them at least) so I thought I would go slowly, export / import categories, then sub categories, then products, then Model/Price/Qty, Model/Category, Model/Attributes, etc. I then would go into the old (1.39h) site & delete all customer orders outstanding (as a matter of routine security, we only keep the last 30 days of customer order anyway) & just export the customer data, addresses, contact details etc.

so, here is my question, will this work? if not why not, what do i have to do to make this method work? any bright ideas? any thoughts, BTW, please excuse the caps in certain locations, kind of fed-up I have been at this for what seems like aeons. Over to you zencart community, what say you?