If you work with a reasonable amount of companies per database (>20) then it might take nearly 1 minute to open form "Business relations details" by pressing button function "Convert to customer" or "Convert to vendor"
Creating the following index may speed up the process quite a lot. So check it out in your test environment first if you like:

“Microsoft provides programming examples for illustration only, without warranty either expressed or implied, including, but not limited to, the implied warranties of merchantability or fitness for a particular purpose. This mail message assumes that you are familiar with the programming language that is being demonstrated and the tools that are used to create and debug procedures.”

Table address

Index Name: RedIDDataAreaID

Index fields: RecID, DataAreaID

Important note: Please be aware that the filed sequence in the new index is important!