A friend of mine is moving from her dads house to her moms(they're divorced) and she doesn't want to lose music and some other files she has at her dads but the problem is her dad has a Mac and her mom has a PC I'm trying to figure out a way she can transfer the files. She wants to send them to my PC first and at a later date transfer them to her moms. Is there an easy way to transfer files from Mac to PC over the internet? I was reading about FTP programs but wasn't sure if that would work Mac to PC. Any help is appreciated.

FTP is machine independent and will work from any platform, but you have to make sure that it is setup on your PC so that you can connect. If you use FTP, both would need to have a highspeed connection and even at that it can take a long time. You also need to make sure that you select "bin" to ensure that files are copied as a binary file and not converted.

Another solution is to create DVDs or CDs, then she would have a good backup. This is the best solution in my opinion.

I've used AIM for transferring files before. She would have to have two accounts, and then sign one on and then do a file transfer. There's no limit to how much you can transfer. Just put everything she wants to keep in a folder and send it.

This can be done, but, very slowly, and often unreliably. Burning to CDs or DVDs is the best bet here.

You could use a crossover cable through your ehternet ports. This will give you a 100Kbps transfer rate and up to 1Gbps trnafer rate on machines with 1 Gbps NICs.
If you have wifi on both computers you can connect them in ad hoc mode. Here is an article describing how to setup the Mac. Here is an article on how to setup XP. For the most point you will assign a static IP to each computer to allow them to connect via their enternet connection. It is the fastest and cheapest.

If you don't just burn a disc, you could plug in a usb or external harddrive or use skype file transfer.