VB.NET: Why cannot copy to temporary directory

I don't know why sometimes when you code for a long period of time, there will be a error that say you file cannot be copy to temporary file.....proj.exe error...

and the whole application cannot run or compile..

the only solution is to copy to another folder and compile it again..

but the error will still occur..

Therefore i can only try one time everytime i compile....

Does anyone know what is the problem behind and how to solve it..

Most importantly, how to prevent in future..

Thanks

Check in ur task manager... sometimes the exe u excute n close sill remains in ur memory therefore preventing the next execution..