cannot unlock a file

Morning all,

Sorry if this is a bit off topic, i wasn't sure which
group was most appropriate, though this seems to be it.

Does anybody know how an administrator can unlock a file
manually in XP Pro? Some program has locked a file and i
cannot do anything do get rid of it. The problem occured
when the program that created the file was terminated
(without error). The program was running on a different
machine however, and was writing the file to a windows
share over the network.

When i try to delete the file, i get an error to say it
is already locked by a user or program, and to sort this
out and try again.

So far i've tried the following:
1. deleting it via 'cmd'
2. renaming it
3. opening/closing it, then trying to delete it
4. rebooted into safe mode and deleting it
5. opening up the remote program that created it, and
trying to get it to delete it again.
6. deleting it via windows explorer

Number 5 was an interesting one, as that program could
not obtain write access to it again either, so it doesnt
look like it still holds the lock.

Anybody got any ideas? This is driving me nuts as it's a
fragmented 300MB file that's causing the rest of the
drive to keep getting fragmented.

Many thanks,
Rolf