trouble with 640GB laptop drive

Need some help with this one guys. Bought a Western Digital 640GB 2.5" laptop drive. With all HDDs till now I've been able to FDISK and format and all has worked well in W98SE. I've done this with drives to 500GB. But this 640GB just isn't acting right. FDISK does not read the size properly though XP or W2K see the 596GB free space just fine. W98 reported size as 128GB or so (???). Ended up partitioning it in XP then formating (FAT32) in DOS, but something is not right!

Explorer can read the partitions, read-write speeds are good but there is some delay when explorer is launched because it pauses to read the 640GB. Tried Norton Disk Doctor, wanted to do a full surface scan and windows blue screened. Scandisk checks run well, even through tens of thousands of files ... but the disk is not right. After writing about 400GB of data tried booting into Xp and it choked trying to read the disk. So did W2K !!! Yet W98 will read it, albeit with a delay. Then suddenly one of the three partitions became corrupted, lost all data and the volume label became corrupted. Can't make sense of it.

Is there a barrier at 500GB over which W98 will not go? I've spent MANY hours trying to get this thing to work properly in 98 but no luck. Appreciate any helpful input.