I still have an XP version running (although am pretty sure it is using NTFS) - the maximum size that I seem to see for any of the block files is 134 MB.
They are named as such:
blk00000.dat
blk00001.dat
blk00002.dat
...
The "reverse" files are named as such:
rev00000.dat
rev00001.dat
rev00002.dat
...
(and are much smaller)
thanks for the response. Googling for the above file names took me to a reddit link mentioning an article "Bitcoin: 285 bytes that changed the world", which was published 4 years ago, and is no longer available. However, I found it in the internet archive and it contains exactly what I was looking for.
For those interested
https://web.archive.org/web/20140213190023/http://james.lab6.com/2012/01/12/bitcoin-285-bytes-that-changed-the-world/