computres behind wrv54g router not available

By pinging the router I assume you mean the LAN side?
Are the firewalls disabled on the PC's. Windows and other software firewalls will block IBCMP (Ping) requests by default.
Can you open the web management console of the WRV54G with it's LAN IP verifying your VPN connection from the remote site?

Yes, my LAN. Firewalls in all machines are enabled (Norton Internet Security). And router says connected and the other side (laptop) says the same.

Logically I should see and map all those behind machines?

You say the firewalls are enabled. If that is the case you may not be able to connect at all. Try disabling the firewalls first.
Also, it is very unlikely your computers will show up when you browse for computers as in My Network Places, and you may not, at this point, be able to connect to them by name. Ty connecting using the IP address in a browser window or in the 'run' box using  \\123.123.123.123

Now I disabled both hardware firewall (router firewall) and software (norton). And found that Norton is the case. All machines were successfully pinged even after I restored router firewall. But I can't live without Norton firewall, how can system working with Norton firewall enabled?

The Norton firewall can be configured to allow services, applications and or ports. I am afraid I don't have it on any of the systems I manage to give you specific instructions. The links below may be of some help as to how to configure though the instructions are for different services. Allowing access to file and print sharing would be done using the same consoles. If configuring by port you will likely need the following TCP ports for file and print services and browsing 135, 136, 137, 138, 139 & 445.

http://symantec.atgnow.com/consumer/resultDisplay.do?gotoLink=16494&docType=1000&contextId=3663%3A16494.16545&clusterName=SymantecConsumer&contentId=3e713185-dfad-4c62-8b53-aed8507f1aa5&responseId=2c6fe064517bb5c1%3A1b1fbf4%3A10a4b8e2c3c%3A-625b&groupId=4&answerGroup=30&score=315&page=http%3A%2F%2Fservice1.symantec.com%2Fsupport%2Fnip.nsf%2Fpfdocs%2F2003120510272036&result=29&excerpt=Configuring+firewall+rules+for+Web-enabled+programs&resultType=5000#

http://www.microsoft.com/windowsxp/mediacenter/extender/setup/firewall/norton.mspx

Read these 3 articles (the 3rd possibly being the solution). It fixed a similar problem for me.

1) NAT Traversal (NAT-T) Security Issues
http://www.computerworld.com/securitytopics/security/story/0,10801,102985,00.html?source=x73

2) KB885407 - The default behavior of IPsec NAT traversal (NAT-T) is changed in Windows XP Service Pack 2
http://support.microsoft.com/kb/885407

3) KB818043 - L2TP/IPsec NAT-T update for Windows XP and Windows 2000
http://support.microsoft.com/?kbid=818043

Sorry... in the previous post, #2 has the possible solution.

Ok, I'll test it. Taking some time.

I couldn't reach to that possible solution cause quickvpn has started to say 'the remote gateway is not responding'. Doubt there's something wrong in my router which needs a different assistance probably.

bluehead, you mentioned above once you disabled the firewalls as suggested everything seemed OK, but you needed help configuring the Norton Firewall. Was the link helpful or are you still having problems?
--Rob

As I said I'm stuck cause quickvpn keeps saying 'gateway not responding' and can't go any further to test solutions. That's the trouble.