Root SD card problems!

Hi all, First of all,please forgive me for asking a probably silly question for my first post! Anyway, I got my new Nexus S in the mail the other day, and its nothing short of fantastic :p I quickly looked up all the cool things I could do with it and I discovered rooting. Btw, please don't take me for a n0ob, I probably sound like one but I do have some limited knowledge about this kind of stuff. Anyway, I proceeded to read up as much as i could, and eventually unlocked the bootloader of my phone from a seemingly helpful guide. I used Clockwork Recovery Mod. A link to the guide I followed can be found here


I also installed superuser following the guide above. This is where my problems start. After this, I started up my phone, and it loaded fine, and i could see the superuser app in the menu. I proceeded to recover all my contacts and previous apps etc, and used the phone for a day. After returning from school this afternoon, I planned to install Cyanogenmod 7. I thought that the best way to do this would be to follow the guide that supplied as i previously used their guide. Link here


I booted the phone holding volume up and power, and proceeded to follow the video instructions. when it it came time to enter the recovery mode, my phone rebooted and instead of initiating clockwork, my phone got stuck on the google screen it shows before booting. I understand now that I was supposed to load my preffered roms etc on the internal storage SD before unlocking, and I can't access the SD card to do so. Every time i try and open it on my computer i get "please insert disk into drive x". I haven't downloaded Rom Manager yet, and i know i need to flash clockwork recovery first, but I don't want to risk doing that then attempting to access the SD card, frankly because i'm a little in over my depth (if you haven't already gathered!).

Any advice would be greatly appreciated as to where to go from here.