Networking a Mac and a PC w/ Windows XP

What model of Mac is it? If it is a G4 tower, adding a second drive is easy. All but the oldest iMacs have firewire ports to add an external drive.

File sharing between OS 9 and Windows is not straightforward. Your best bet, if you decide to go that route is third party software like Dave from http://www.thursby.com

See also http://www.macwindows.com

It is a PowerMac 3.  Pretty old school.  It is OS 9.0 and doesn't have any expansion slots nor usb slots.  I can't put another hard drive in it either, no room.

I have never heard of a PowerMac 3. Are you sure that is what it is? Is there a name on the front of it? Can you describe it?

Maybe there is a model number on the back?

Can you perhaps identify it from this:  http://www.info.apple.com/support/applespec.html

http://docs.info.apple.com/article.html?artnum=43122

I guess the closest is this.  This thing is accient though, they are too cheap to get a mac mini or something so I need to get a way for this to get more storage.

If that is what it is, did does have an external SCSI port, so an external SCSI drive would be a possibility. Either that, or put in a larger internal drive. The internal drive is a standard IDE drive, so any PC style drive will work.

Networking through ethernet and tcpip is always a possibility. Anything above OS 8 will allow TCP/IP. You can establish a webshare on the mac with FTP capabilities and share files with the pc that way. Worked for me in the dim dark ages. Pc will recognise the ftp share in IE and you can use IE to drag and drop FTP files. make sure the permissions allow and MAKE SURE this is behind a firewall. NO external Ip addresses unless you want lots if unwanted files very quickly.

To get more storage on the Mac, as already suggested, an easy way is to put in a new hard drive.  However, the BIOS on the Mac will only support fairly small drives, so bear that in mind.  

If you were running OS X (up to 10.2.8 supported, I see) you could then easily pop in most any PCI USB card, and then plug in any USB hard drive - that would be easy....but it requires OS X for USB card compatibility (it natively supports most generic USB cards.)

I don't think using FTP is a practical way to get more storage. "Storage" to me implies immediate and easy access using the normal finder.  FTP doesn't really offer that.

The G3 All-in-one will support drives up to 127 Gigs.

It does have 3 PCI slots.

OS 9.1 supported third party USB cards, and the update from 9.0 to 9.1 is a free download:  

http://docs.info.apple.com/article.html?artnum=75103

Upgrading to OS 9.1 is strongly recommended anyway as 9.0 had serious bugs that 9.1 fixed.

Mac PCI bus USB 2.0 cards:  http://www.welovemacs.com/adapters-usb-or-scsi-adapters.html

Exactly (strung's post is correct) - you'll need to stick with smallish IDE drives.  

Also, bear in mind if you make this your boot drive, you'll need to partition it so that it has the first boot partition in the first 8G of space:

http://www.lowendmac.com/ppc/g3aio.shtml

There are issues with "large" hard drives to watch out for...nothing big, but just be aware of them, or stick with small ones under 120GB, and partition them - or stick with really small 8G drives. :)