Root partition full of files in /var/lib/postgresql/9.1/main/pg_xlog

Hi admins
I'm a newbie, I hope this is the right group and admit I have little
postgres experience. I'm working on a VM I can easily re-install so
killing it doesn't matter. The dir is full of 508 files, the last few of
which look like:

-rw------- 1 postgres postgres 16777216 Aug 25 02:19
0000000100000001000000FA
-rw------- 1 postgres postgres 16777216 Aug 25 02:39
0000000100000001000000FB
drwx------ 2 postgres postgres 4096 Jun 13 13:24 archive_status
root(at)operations:/var/lib/postgresql/9.1/main/pg_xlog#

I have root access to the machine but I don't have any postgres access,
other than sudo of course. I've tried stopping my app, ensuring nothing
postgres appears in ps and tried deleting the files but when I restarted my
app, it didn't work. I've checked (Google) as many posts as possible but
can't find exactly what I need, i.e. the method of removing the offending
files cleanly.

Here's as much as I can tell you
Debian 64 bit running on ESXi
postgres 9.1

I have some *nix experience, can use vi and sudo and the like

I hope you can help
Thanks