how can we install applications & ringtones on the MMC??

When you have a writable memory card installed, and you install an application, the installer on the phone will ask you whether you want to install it in phone memory or the memory card. If you want to move applications you have installed, the safest and easiest way is to reinstall them.

You can also store ringtones on the memory card (just put them in E:\Sounds\Digital on the card). You can move/copy them locally on the phone, if you install FExplorer (http://www.gosymbian.com) on it.

I bought a USB card reader for my MMC which is much faster for transferring Mp3's and other crap onto the card. For installing applications you still have to go through the Siemens Data Suite.

I make my own ringtones, usually out of songs I like. I use the Marvintec product (do a google search, acxtractor for ripping mp3's) which lets you make an mp3 of a portion of a song (like track 3, 15seconds to 25 seconds). Then I use a converter (again, available free, do a google search, mp3 wave converter) to make it a wav file. Then I put my MMC into my card reader, go into Windows Exploder, and drag and drop the new wav ringtone I made into the sounds/digital directory as someone else mentioned. From there I can add that ringtone to my profile, or to individual users. I have some Simpsons wav files as certain friends' ringtones and Ozzy Osbourne "Crazy Train", U2 "I Still Haven't Found What I'm Looking For", and Billy Idol "White Wedding" song snippets as my other ringtones.

You don't have to install via the SDS, thats a load of tosh.

Copy the .SIS file onto the MMC, then in either FExplorer or the built in File manager, just run the .SIS file - it'll go ahead and install.

The alternative route (which you have to use with much larger apps) is to use UnmakeSIS to "unzip" the SIS file. Then copy the files straight into the \system\apps folder on the MMC ....