If you’re using Vista:

C:\Users\**YOUR NAME**\AppData\Local\Rockstar Games\GTA IV\savegames

If you’re using XP:

C:\Documents and Settings\**YOUR NAME**\AppData\Local\Rockstar Games\GTA IV\savegames

Formatting your C: Drive deletes EVERYTHING on that drive. It wipes it completely clean. Formatting your C: Drive will delete your saved games lol

Yes they will.
There should be located in the Grand Theft Auto 4 folder in the Program files.
Go to My Computer, then C: drive and the folder Program Files should be in there.
Hope this helps.
The game will also be deleted if you format it.