I thought this would turn out to be a "find the song" challenge rather than a "make the song" challenge. I did search for "when I'm running windows" so of course didn't turn up "reinstalling". I thought up these bits in the bath:

Mac is fine for flakes and fruits
Linux users pick their snoots
But Billy Gates is coining loot
When I'm etc.

Macs are at your call and beck
Linux runs as you'd expect
I utter stronger oaths than heck
When I'm etc.