You might have Speedtouch router which acts as DSL modem and digi-TV bridge and also offers you internet. Now you want second router like Linksys WRT54GL to serve your needs better.
Speedtouch has ip 192..168.1.254, linksys factory default is 192.168.1.1. If you take cable from your computer and stick linksys between modem and computer then your computer will not get any internet. This is because speedtouch and linksys networks “collide”. You cant change speedtouch network but you can change it for linksys. You must change Router local ip address some other than 192.168.1.XXX eg change it to 192.168.5.1 and enter to gateway your speedtouch modem ip 192.168.1.254.
Save, apply and reboot and you have yourself internet through 2 routers.