Foolproof Outlook Express Backup

I have been asked to transfer data from a Win98 system to a new XP m/c and the Outlook Express data is of the utmost value in this case. I have tried the odd utility in the past and have found that they do not meet expectations. E.g loss of address book etc. The existing version of OE is V5.0 and the new m/c has v6 (or so I am told but I have not yet visited)!
Is there a foolproof method of backing up all OE folders + address book (whatever version) and then guaranteeing a restore to the new XP system. If it fails I’m toast!!!