When I load the game sometimes no sound! How to install oalinst.exe? Or the reason in other? Maybe I should buy an external sound card? Window 7, 64 bit

What you have sound card?
You try both cohokum.exe and COHOKUM_DS.EXE ?
Oalinst download from here and just install https://drive.google.com/file/d/0B7r13zct35kHaTBWV0JIUTM4aUk/edit?usp=sharing

My sound card is integrated in motherboard. Oalinst.exe I installed,when I installed Apache Havoc. I remember that in the first versions EECH,integrated sound card was working badly,and if you put another sound card,the sound was better!And now I repeat,I sometimes turn on the game and the sound is there,all right.And another time when I turn on the game,no sound!

Yes, every good separate sound card is better. I use old audigy 2 value, and no have problem.
You can try change in eech.ini hdwrbuf parameter.

and what you put option in eech.ini hdwrbuf? I was 50,shifted to 0,tried several times to turn the game and the sound is good

i have 50,but i have good sound card,for you probably better is 0 or 2 ~ 10