For how long has .cvd been the format for database files ?
Clamwin 8.7 issues an error message "Invalid database format" when I try to use it with
the latest databases.
BTW-my reason to try an earlier version is that the most recent are noticeably slower in
this computer (PII 333 MHz, 32 Mbytes RAM,Windows 98 last updated in july 2006) .

you may need to re-download it, by using update feature
pls check that is enough big (~5mb for main and ~1 mb for daily) and something in between has not screwed it (maybe a transparent proxy that denies it with an html page)

Sherpya said:
"You may need to redownload it, using the update feature..."
Redownload the database or or the Clamwin executable ? BTW,
the extremely slow download speed while using the auto update
feature in Clawin ,which I mentioned in other thread, still persists .
Perhaps this is a connection problem , but I cannot do anything about it.
I have to downlad the database from a mirror using the IE or Lynx download
functions.

you should redownload the db, you can manually download the two .cvd files and put in the db dir

Sherpya said:
"You should download the db"
Excuse me for the ignorance, but is there a database which is not contained in the .cvd files ?
I did not see any such at the mirror sites; only main.cvd and daily.cvd .

go here: https://www.clamav.net/
download main.cvd and daily.cvd ("save target as"), links you will find below Project News
then put them in your database folder.
and yes, there are some unofficial database files.
also everyone can make his own database files, it is explained in a few places.

But this is what I did and the reason why I started this thread is that Clamwin 0.87 returns
an "invalid database format" error message when I tried it with those files.

try opening the .cvd files with a text editor such as notepad, maybe you get a proxy response instead of the actual file. Nothing changed in 0.88.7 to cause this. You can try to install 0.88.6 and see if it accepts those files.