Do you have an MP3 player?

[Harrison]

With my tape and CD () players, I can store as much as I like on tapes and CDs, and just change them when i like. This is dead easy. It would be a similar case with a small MP3 player, but changing the music would be awakwardas I would have to get it onto the computer, and transfer it to the player via the computer.

No need. You can get MP3 players that use SDCards so you can just copy the music you want onto a series of cards and then just swap them over to load more music. And with SDCards now being so cheap (£3-7 for 1GB) it is quite a good solution if you want a small MP3 player that has no moving parts, so you won't be so worried about dropping it, and no moving parts mean much longer battery life.

But obviously this isn't a problem with big ones as the music can be left there permanently while new music is added, rather than having to change it.

Exactly, and with 60GB+ HD based MP3 players you can fit a lot of albums on them and not ever need to worry about never having something to listen to.

Do most HD based Mp3 players have removable HDs these days, so you can put a bigger one in, and also do they have FM/AM radios and removable batteries?

Nope, I don't know of any HD based MP3 players where the HD is removable. They all use custom software with custom formatted HDs so swapping them over wouldn't be straight forward. With some it is possible as much like most products fans have hacked and experimented with them to make it possible, but obviously it voids any warranty.

As for Radios, it depends on the MP3 player. Many do, many don't. You just need to show around and find one that does if you would like radio built in. And many that do have it allow direct recording from radio to the storage (HD/memory).

Regarding batteries, again some have removable batteries, and others don't. This has always been a complaint of iPods because they all have fixed batteries that can only be replaced at the factory so cost the owner money to have it done. Some smaller flash ram MP3 players are powered from a single AA or AAA battery so it is easy to replace it if you run out of power whilst out. But most are rechargeable and are similar to mobile phone batteries. They all last at least a few hours between charges so you don't need to worry about batteries going flat. And they either recharge from a charger or docking station or via the usb port of your PC. Not really an issue.