yulwei: it would be excellent to note whether or not the suggestion helped, or whether you have otherwise solved this situation...
Sean38FL: I know this is such an old thread, but I wanted everyone to know is I was having trouble transferring from XU4 to Ultima 5. I first tried extracting the party.sav file from the Ultima 4 zipped game file, that didn't work. Then I tried mounting a drive as A and copying party.sav from the Users\<Username>\AppData\Roaming\XU4 directory and transferring from there, still didn't work. Then I tried copying party.sav from the Users\<Username>\AppData\Roaming\XU4 directory and copying it into the Ultima 5 directory and pressing C as my floppy drive and that worked. I didn't even have to run FIXPARTY.EXE. I hope this helps someone who's having trouble.
I just wanted to say thanks, this worked. I found your answer from searching google. I played U4 with XU4, and using party.sav from the standard xu4 folder does not work for transferring your character to U5, you need to use the party.sav from the appdata/roaming/xu4 folder.