Have a shower.

You enter the bathroom to find it filled with steam. You are obviously not the first person to come here today, and you're not complaining. The warmth here is offsetting the cold in the dormitory. You choose a corner which no one else has claimed, and place your clothes and towel on the bench. Then, you quickly undress, and wrap your towel around your waist. Turning, you almost walk straight through Moaning Myrtle.

"I've been murdered", she wails.

While technically true, her high-pitched voice is grating on your ears, and Myrtle's **** took place decades before you were even born.

"I didn't even walk through you", you protest.

"Harry Potter", Myrtle says, swooping around you. "It's been a long time. You never visit my bathroom."

"Oh. Um. It's a girls' bathroom, Myrtle", you say quickly, before she gets too offended. "It would look suspicious if I went there."

You pause as a thought strikes you.

"What are you doing in a boys bathroom?" you accuse.

"I'm just looking around", she says, with a wink at you.

You shudder, and decide that in the future, you need to check the bathrooms thoroughly before you get undressed.

"If you visited more often, we could chat", Myrtle suggests, unsubtly.