Convert a wireless router

to a wireless AP (Access Point)
While connected to the main router go Start then Run in XP - (Windows key plus R in Vista and Windows 7), then type in the following, including all the spaces:- cmd /k ipconfig /all -- then press Enter and from the black form that shows up, take a note of the numeric code beside the word "gateway" -- usually something like 192.168.0.1. Type exit to close the black form.
Now connect the router to be converted only to a computer via network cable and log in
Setup the wireless security
Disable the DHCP and change the LAN IP to match the gateway IP but ending in something like .253
Finally connect one of the four LAN ports of the AP to the main router, do NOT use the WAN port.
Connect Old Linksys Router as a wired (and maybe wireless) Access Point
1. Just got a new DLINK Xtreme N DIR-825 Router. Directly connected this to the internet.
2. Currently, the Linksys WRT54G (1st Generation) is connected to the DLINK by an Ethernet cable to one of the 4 ports on the back.
3. The Linksys further splits the signal to another 2 computers and a NAS by hardwire.
4. The internet is still getting through to all the computers, but the computers are not able to access the NAS or each other.
5. I can't seem to open the WRT54G's access (192.168.1.1) because (I thin) the new DLINK uses a local set of IPs that are 192.168.0.1xx.
Weirdly, I can login to the NAS using its IP, and I can see it on the 'Network Places' of the computers ,but when I try to connect, it says the drive is moved, etc. etc.
I use a variety of computers / O.S's on this system: XP (2) hardwired, Win 7 (2) hard wired, Win 7 (1) wireless, Mac OS X Snow Leopard (1) Wireless, plus various other wireless devices (phones,Wii, etc.).
NAS is a Synology DS411+
Hope someone can help me:
1) Get logged into my Linksys
2) Get the NAS accepted by other computers on the network.
Answer
go Start then Run in XP or
Windows key plus R in Vista and Windows 7
then type in the following, including all the spaces:
 cmd /k ipconfig /all
then press Enter and from the black form that shows up, take a note of the numeric code beside the word "gateway" -- usually something like 192.168.1.1.
Type exit to close the black command line interface.
Connect only a computer to the router you are trying to convert to a AP and log in
Set up the wireless security
Disable DHCP and change the LAN IP to match your Gateway's IP but ending in .253
Now connect one of the four LAN port to the main router via network cable.
I suspected i had to connect a computer directly to the Linksys I want to use as an AP.

To disable DHCP and change the LAN IP to match, it  means on the AP router!