Memory allocation in .net

Question

I have a C# exe application ,in which i am using memory in terms of string.I have my 65 instances of my exe applcation runnning simultaneosly.So is there any issye of memmory wastage or memory is deallocated or memory is released by strings variables once exe applcation execution completed.
I know that .net has a CLR and garbage collector but i am not running my applcation on .net framework.It is running on OS by sechduling exe in task manager.So please clear my cancern?