i cant remember how to do it

Hi, so i have a problem i cant remember how to solve. i want to open a text file and the directory is "C:\users\michael\desktop\test.txt" but it wont open obviously on other comps because the directories are different. how do i open it when the subdirectory "michael" will be different. im sure i used to use something like "C:\users\MyDir\desktop\text.txt"
many thanks