You can get the machine part hidden in one of the inner tubes in Misty's Gym.
If you get the machine part you can go to the Power Plant and give the people the machine back.
Then go to Lavender Town and go inside the Radio tower. They'll give you a Kanto Radio Card.
Then go back to Vermillion and use your radio and find the Pokeflute station. Play the music and interact with Snorlax. It'll wake up and attack you at lv. 50.
After you passed through go inside the Diglett cave. You'll end up in Viridian City and head North and you'll be able to fight Brock.
at the end of the cerulean cape (route 25)
You best the rest of the Kanto Gym Leaders. Since they are challenged in no particular order, Misty may be your Seventh challenge. If this is so, then you go to Cinnibar Island, where you find Blue (Gary Oak's game counterpart). He is the Viridian Gym Leader, and you take your 8th gym challenge. If Misty isn't your 7th challenge, then you beat the other gym leaders before you can challenge Blue.
Once you fixed the Power Plant, go to the end of Route 25. Talk to Misty and she'll return to the gym. Then you can beat her. (She uses water Pokemon so I suggest you use grass or electric Pokemon.)
You could buy it at the Goldenrod City Department Store.
Catch em' all! You can go to the cave around Misty's gym and get yourself a Mewtwo.
misty will be a gym leader in HeartGold and SoulSilver
route 25
After you defeat Misty, You can go catch suicune by Bill`s house.
Misty is at the Cerulean Cape. It's close to Cerulean City.
Misty has a 49 Golduck 49 Quasire 52 lapras and 54 starmie
She's at the end of route 25
top of rout rout 25 =]
misty
you cant
Route 25, near Bills house.
at the end of the cerulean cape (route 25)
Talk to mr. Pokemon after beating game and capturing lugia