Git pack - repo size doubled

I'm using git version 1.7.3.3 under cygwin (W XP64). When I tried

git repack -A -d --depth=255 --window=255 --window-memory=4g

I've got the message

rm: cannot remove `pack-c75642be5314b1a98ddfcf0d51ac838db4af75ad.pack':
Device or resource busy

It seems like the file hadn't got closed. The non-deletion of the file
roughly doubles the repo size (134070 KiB instead of 67470 KiB).

- Can I manually remove the file?

- If I do it, does "git fsck" suffice to make sure, everything's all right?

- Would creating of multiple packs work better? What "--max-pack-size"
would you recommend?