mozilla emails on an old pc to a new with xp and thunderbird

i have tried and evidently i am a stump ai i can't figure how to do this.
i have googled and sent hours trying to move years of old emails to the new pc.
i can't go abck to the old pc to use for email, as it was win98 with a dialup account and the xp is dsl --- 2 different isps.

you are my last hope before I scream and pull the last of my hair out.

i guess i could file save as the email messages on the old pc, but it seems that might be a file save as 2,000 times

 

Probably, this link from Ramona's Netscape Solutions is the best. What is said applies to the NS6/7, Mozillas and Thunderbird. It is imperative that you don't store old mail in a single folder. The Inbox is not a storage file/folder.
And, of course, in order to do manual transfers, one must realize that the old OS do not hide the profile folders, while WinXP does (note the link about Profile location in the above given link)

 

Try mozbackup, add-on from mozilla site. Assume t'bird on both!
Install on both systems, create back up on earier and either use network, x over cable, floppy,usb stick rwcdrom or whatever to transfer restore to new sys, can also txfer themes addons

hope this helps