This is what i would do with a spare 54GB:
Linux swap (which requires its own partition): double your RAM but no more than 512MB. The 'double your RAM rule' was important whem RAM was at a premium but not so much now. I have 1.25GB RAM and a 512MB swap partition. The system _hardly_ever_ needs to make use of it. Don't worry about the filesystem, it is set automatically.
You can do a full, complete install of Mandrake in 5GB, I'd suggest that amount as '/' (the root partition), go with the default filesystem, which is ext3.
Depending on the amount of personal data you keep, the same again for /home, on its own partition, default filesystem is ext3.
For a FAT32 partition readable by both windows and linux, again it depends on your needs. I would suggest at least 1gb so you can fit an ISO on there.
Then you still have loads of space for any other storage, other distributions and so on.
Your modem *may* be problematic. Search the forum if you get stuck. Or buy an external serial modem - guaranteed to work.
Your graphics card - no worries. A bit scary to install the driver if you've not done it before; again search here and read nvidia's documentation - its actually very good.
Mandrake's partitioning tool will only mess up other partitions *if* you tell it to