Where to find the program for selling the large amount of goods in the store?

I have Russian program ¿¿¿¿¿¿¿¿ (www.pimarket.ru) assigned for selling goods in the store. I have a very large stock of commodity and now the program is working too slow. I supposed that the program is written on Visual Basic, because the database is Access. I'd like to find a simple and efficient  program that is able to sell a large amount of goods and keep records of such a chain of operations as "Input article"-"Selling"-"Closing of checked days"-"Retrieving the amount of each item of the goods". In other words the program must maintain all the common trading operations and simplified calculation of the shoppy items. It is desirable that a program could work without making out a bills and invoices and the user could work with it without deep knowledge about sophisticated accounting procedures. I could not find similar program to ¿¿¿¿¿¿¿¿, so please suggest me more powerful program you may be know!
TIA!