Hello,
Our company developing a new software for our devices.
One of the importent issues is choosing the right DB.
The requirements: simple, easy to maintanance, quick to develop.
support multiuser enviroment, and remote stations.
Thousands of records to be stored.
Will be accessed by dozens of threads simultaneously, writing and reading data.
I would appreciate you help.

based on that information

Anything other than flat files will do.

Well, not exactly...

Access doesn't fit because he doesn't treat multiple read-write very well.
SQLite and compact SQL won't fit as well.

I can't decide between SQL Express 2005 and MySQL...
Because from one hand it's important that the installation will be fast and simple (which is the case with MySQL), from the other hand it's important to be able to program and maintain it easily and fast (which is the case with SQL Express 2005).

maybe you have a tip for me?

Or maybe I'm missing something and there is anothere DB I haven't thought about?

Access doesn't fit because he doesn't treat multiple read-write very well.

Writing efficient queries to open and close the DB as quickly as possible and it can. The majority of "problems" with Access are usually created by slip-shod programmers.

BTW is this for a web application or a desktop (LAN / Intranet) application.

For maximum portability I don't ever see myself using anything other than Mysql.

Access doesn't fit because he doesn't treat multiple read-write very well.
SQLite and compact SQL won't fit as well.

Well, Acess is a software built around the JET engine, and not designed to be used in an highly parallalized environment.

SQLite can, but as it's working on a binary file, it does read lock on every insert or update that is sent, whcih can impair throughput on really really busy sites.

If I where you, I'd avoid sql express 2005.
It's not a bad product, not at all, but if you go the sql server road, go with sql server 2008. It exists in express edition too.

Personally, I'd choose postgresql.
http://www.postgresql.org/

It's a relational DB engine that have more than 12 years of development behind it.
It's fast, flexible and stable with a native Windows version.
Support a whole lot of extended features, can be easily setup in a replication mode and distributed nodes.
http://www.postgresql.org/about/featurematrix

The same to sql server, yes, but where the sql server express edition is limited (memory, number of cpu used), postgresql is not.

I work as an sql server DBA, and one of my co-worker is that kind of person you refer to with "the guru".
That guys seems to know everathing about sql server, and it's really impressive to work with him.
I presented him postgresql once, when I just arrived in the team, and he's comment after 2 hours of play with it was

it's a pretty impressive software.

Already way more than I was expecting...

Ordinarily, I'd agree 100% with the PostgreSQL suggestion -- but I'm not sure,based on the Nlobak's 1st comment: "developing a new software for our devices". If you are looking for an embedded db, then PG can't help.