Does the Macintosh HD has any bad effects on the computer?

Macintosh HD is your system OS on your hard drive. Without it, your computer would not be able to boot up or run or do anything else.

So, I do not understand your question - please re-post what exactly you want to do and include your device model, year, and current OS version.

Be more precise and specific about what you are asking. Macintosh HD is your drive, and you don't download it. If you mean "download to" then the answer is, it's OK.