Funny but on my 4GB of 1066 memory the game lags as hell in 10 seconds interval.
There is FPS drop down and hard disk reads and reads.
Any solution?

I'm at a loss on this one and haven't heard of any issues like it so I'll be grabbing straws here.

What is your page file like? Under windows control? Have you turned on hyperthreading for your cpu(s)? I did that recently and got DB running really smooth, although my slowdowns weren't nearly as dramatic as yours. Have you upgraded DB to 0.74?

If you activate Task Manager and see what pops up to the top in CPU usage, you should have a good idea of what's doing it. It might not even be DOSBox related, we had a virus scanner wig out on us at work recently. It never sends up a red flag, it just decides to take all available resources.

Windows-Key+R>Open: taskmgr

I solved the problem. Earlier i set 1280x1024
now I have 800x600 and everything is OK.
What is more I think that a few years ago I found a copy of Blood where I could set 1920x1200.

Your found copy I assume was not being run in DOSBox and prob in a native OS.

You could also try using the SVN version of DosBox. Can be found at www.emucr.com. Just a little caution it breaks the CD initialization. Gonna find some way to fix it.

http://www.gog.com/en/forum/blood_series/a_custom_dosbox_build_to_improve_the_support_for_blood Maybe that one helps ?