How many MB's or GB's would the file in notepad that just has the number googolplex written in it be?

You're probably imagining the number written out in a string of zeros, NOT in exponential notation. (Notepad doesn't handle exponential notation anyway.) The definition of 1 googolplex is: '1' followed by a googol zeros. In an ASCII text file, each character is represented by one byte of data. All the data in your file consists predominantly of the character "0", and there are a googol of them in the file. So the file size must be roughly one googol-Byte. 1 googol is 10100. A good sized hard-drive holds 1 TB = 1012 Bytes. So your Notepad file would fill 1088 1-TB drives ... more than have ever been or are ever likely to be manufactured. Let's not even think about the time required to save or retrieve the file.