I would have to tell you not to dispair as not all companies are the same. What settings are you looking for? I personally left 123-reg a few years ago for a different reason.
I know this will not help you now but for future reference I would offer 2 tips:
First of all, use a hosting company that offers cPanel. That way all the info you would usually need is your cPanel username, password and web address. You would also quickly remember the cPanel port number as 2082.
Second tip which is invaluable is to partition your hard disk next time you reinstall Windows. Then store everything important, documents, media, settings etc on D: as this acts as a completely seperate hard disk and will not be affected by future reinstalls. You can even set "My Documents" to automatically store everything there. If you have a brand name PC recovery disc the option to partition may not be abailable. If so and asuming you have Windows XP home you can get a generic copy. This would be easily available using your imagination. You can then use the COA sticker on your PC during install and activate as normal. Some drivers would probably need to be installed so get all available drivers first from the PC manufatuures website.
Hope this can be of help in the future.