hi,
I wrote the code for SPI Port ...

I wonder - why do you think that MultiMedia Cards use SPI interface? For example, looking at AT89C51SND1C datasheet (8051 with MP3 decoder and alot of interfaces supported include USB,IDE/ATAPI, I²C, SPI, I²S/PCM and MMC as well) I read next:

MultiMedia Card Controller
Card Signals.
The communication signals are:
• CLK: with each cycle of this signal a one bit transfer on the command and data lines is done. The frequency may vary from zero to the maximum clock frequency.
• CMD: is a bi-directional command channel used for card initialization and data transfer commands. The CMD signal has 2 operation modes: open-drain for initialization mode and push-pull for fast command transfer. Commands are sent from the MultiMedia Card bus master to the card and responses from the cards to the host.
• DAT: is a bi-directional data channel. The DAT signal operates in push-pull mode. Only one card or the host is driving this signal at a time.

So I doubt that simple SPI usage helps you; in my opinion it takes more complex programming if your MCU does not support hardware MMC interface.

Regards,
Oleg