1 modem 2 computers, 1 LAN......can both connect at once ?

Yes it is possible.  There are several ways.  Easiest is probably using Win98 Internet Connection Sharing.  There are several hardware configurations possible including two NIC cards and a crossover cable (fastest connection), a direct cable connection, Infrared connection, etc.

Bert

if you don't have Win98 second edition, this feature is also available through many third party programs.  Ishare and modem share are good but I found wingate to be the best.  http://wingate.deerfield.com/

for info on win98se modem sharing:
http://www.annoyances.org/win98/features/ics.html

personally, though it is stable once setup, I find 98se's version to be harder to setup than the others.

Another program I have used under Win95 is HTPROXY.  It is a little tricky to configure but it works well.

Try www.tinysoftware.com

dcollis, you will nead a network card in each computer. Using a crossover cable (specially wired or available from a computer store) you can network the two computers without a hub. In addition you will need a proxy server program to access the net from the computer without the modem. There are many programs available, both free and for a cost. I use a freeware program named Vsocks Light. It is easy to set up. It is available from http://www.pscs.co.uk/software/downloads/vsockslight.html
In addition if you are new to networking you will need to set up the computers. Instead of going into considerable detail here, I will point you to a site which I have found extremely useful: http://ourworld.compuserve.com/homepages/J_Helmig/faq.htm
Work your way through the pages. In addition there is also information about setting at Vsocks, of which adds to Vsocks help pages. It is a little difficult to find, therefore here is the url: http://ourworld.compuserve.com/homepages/J_Helmig/proxyins.htm
Good luck and please ask if you need further information.

In my company, more than 20 peoples are sharing two modems to access Internet with the help of SyGate(www.sygate.com). It has many powerful capabilities, such as built-in firewall, auto dial-up, and auto disconnection, etc.

Good lock.

Have a look at WinProxy Lite also:

http://www.ositis.com/wplite.htm

You can do -
1. Dial up networking modem sharing in windows 98
2. wingate - can download from www.deerfield.com demo to work on one machine and see how it is - doesn't require much config at all only pointing to the dial up networking connection if you are using it only as a gateway.
3. Modem sharing software - don't know much about this one!

Cmap,

Hi, I see you are new here.  WELCOME!  There are some unwritten protocols followed by us here on Experts Exchange I thought you should be aware of.  First, we usually don't post answers until the questioner asks someone to because doing so locks the question, making it difficult for others to see and offer help.  Second, posting answers is not even necessary as the questioner can accept any comment as the answer.  Finally, it is unacceptable to repost the comments of others as an answer at any time.  Now would be a good time to unlock this question by choosing the option to "Change your answer to a comment"

Again, welcome and good luck.

Thanks
Bert

1cell answered my question first, so post an answer and you will get the points. It was just want I needed, Thanks.

dcollis,
You will need to reject the pending answer before anyone else can post one.  Also, you can accept 1cell's comment as the answer after you reject cmap's answer.

Bert