Hi~not been on here for a while (took me an age to remember log in etc!) which is a good sign as everything has been ticking along quite merrily...then I thought I would catch up with 21st century and the fun began

Ok~I have just purchased a 'Belkin ADSL modem with wireless G router and wireless G usb network adapter', was so proud of myself until I wanted to intall it etc.
It would seem that I have the wrong modem~I presently have an ADSL speedtouch which has a fixed connection into it so am unable to use etheral wire. (I've confused myself already!)
I have an old 105 Voyager that I was given when I was with BT but it won't let me install it, even using disk I still have (tried it on notebook laptop too~keeps telling me I don't have administrator rights blah blah blah).
I am currently getting my broadband from Orange~If I upgrade with them they want to charge me a small fortune initially and then monthly which I have told them to poke!
*Is there anyway of using present speedtouch with belkin wireless?
*If not, if I purchase an ADSL modem (without a fixed connection!) what do I need to do then!? Uninstall speedtouch-install new modem? But will my Orange broadband still work if internet connection not 'coming through' Orange provided speedtouch?
*If need to buy different modem, where is the cheapest/best/easiest place for me to go either on foot or online?
Sorry it's long winded but it's late and it's been driving a little crazy! Thank you.
Lara