Need step by step for new OS load?

I need to get an OS for a Dell Latitude CS PII 400MHz 128MB 6.49GB 13.3 Laptop, I know it can't support anything above Win 98 but this only needs to function for Internet. I am happy to consider any OS but I have to be able to download it to a USB thumb drive, the old Dell does not have a CD drive. Please, please... any help is greatly appreciated!!!