Really depends on what you have available to you. Obvious options are as follows:
- Network file-sharing through a >1000Mbit network
- Plug laptop drive directly into desktop motherboard (through use of adaptor if IDE, otherwise just via normal S-ATA)
- Put laptop drive into a external 2.5" enclosure (USB 2.0, IEEE1394, eSATA) or vice versa using desktop HDD in external 3.5" case
- A/A, PC2PC USB 2.0 transfer cable
- Many many cycles using a removable disk
Do you require to copy entire partitions including MBR, boot sector etc. as well so you can boot off the laptop drive afterwards (transfer entire OS & installation)? Or do you just need to transfer 'user data'?
Those are a few ideas.. If you want a more specific answer, you'll need to give more specific details.