gnus .marks, .overview

[imputerate]

 thanks for helping me get back into gnus; i still have a big
problem:

 1/ now that i'm back in gnus, i find 9520 emails, and counting, in
my
nnml+privat:mail.misc
file;

 2/ i finally got access to them,
BUT

 3/ i can't restore the marks which had tagged as "deleted" all
but
220 messages, when my ubuntu box and, with it, gnus, crashed last
week;

 4/ i want to get at the 220, so i can delete most of them and
archive
the improtant
ones;

       [i archive important emails in an old babyl tree i've had for
16
years, long before i switched from emacs/rmail to
gnus;]

the relevant files
are:

  -rw-r--r-- 1 hodgson hodgson 25 2008-05-18
00:47 .marks
  -rw-r--r-- 1 hodgson hodgson 2895 2008-05-15 19:13 .marks.
20080517
  -rw-r--r-- 1 hodgson hodgson 21 2008-05-17 15:38 .marks.
20080517b
  -rw------- 1 hodgson hodgson 2646578 2008-05-18
15:06 .overview
  -rw------- 1 hodgson hodgson 2621558 2008-05-15 19:12 .overview.
20080517


i have read the manual and googled them, with no luck finding out
how
they
work;