can't find ubuntu on local network

The connected medium is moot, as long as the adressing is fine it will work. Have you shared folders on the windows system(s)? What version of windows are the systems running?

Ubuntu laptop can see the windows machines, but windows (both using XP pro) doesn't find Ubuntu.

by the way...
Ubuntu is on a laptop with windows 7

Can the XP systems ping the IP address of the ubuntu system. You can find the IP address with:

ifconfig | grep addr

Should show it.

i don't understand the question

ifconfig is unintelligible in windows XP

Sometimes name resolutions in Linux don't work. So if you use the name in the connection it will fail because the systems cannot convert the name to an IP address. Computers don't use names, they use IP addresses.

If you use the IP address instead of the name, it may help

ifconfig is to be used in UBUNTU. Once you get the IP in Ubuntu you can contact it in XP

that's ok. i give up

again...the laptop with ubunutu is shared with windows 7. it isNOT standalone. the windows hard drive is found on the network. ubuntu is NOT.

again...personal file sharing preferences cannot be activated because required packages are npot installed on the system.

going to try one more time to explain this:
desktop computer...windows xp pro
laptop computer windows 7 and Ubuntu residing on same hard driver.
ubuntu can find windows xp pro hard drive no problem. see all files which are shared.
windows xp pro cannot see ubuntu.
windows xp pro can se windows 7 public shared folder.
under ubuntu system->preferences->personal file sharing the entire top end dealing with file sharing checkbox
is greyed out. Box says "required packages are not installed on system.

what are the packages Ubuntu needs??????

So is this a dual boot?If so then you will need to have used ext3 for your Ubuntu partition and the default is ext4. Windows is pretty pisspoor and can only access Windows based file systems. If you only have one drive (not driver) and are choosing between the OSes at boot then yes, XP and Vista can read each others files as they both can read NTFS which bot of those use. Ubuntu can read and write NTFS too. Windows cannot do anythingwith Linux based file systems despite the definitions being available and they could easily incorporate it into their OS, but they don't.

can i change to ext3 or is it too late?

Yes, if you create a journal you can convert ext2 to ext3 easily.

pls explain how to do it

sudo tune2fs -c 0 -i 30 -j /dev/hda10

assuming /dev/hda10 is your ext2 partition. You can tell which it is with:

sudo parted -l

just checked with car /etc/fstab and found it is ext4

that's cat...
anyway, just tried sudo parted -1 -l and got nowhere

just found disk /dev/sda: 250GB