OK I'll try to be quick, I live on the east coast of the US its only 5 pm here so I know its late in the UK (About 10 PM) But anyways... If the actual program of iTUnes is gone, like no iTunes icons or an icon you click and nothing happens you will need to do a clean install of iTunes.
First goto control panel>add/remove in windows and remove or try to remove BOTH iTunes and quicktime if listed there. Now you will goto this link and roll down to the section "Clean up iTunes installer files on the computer" and follow the steps there.
http://docs.info.apple.com/article.html?artnum=93976
After that disable any antivirus/security/norton/mcafee programs running in the system try (In other words any antivirus/security icons that show near the time clock in the bottom right corner of windows, rightclick and turn off/disable) and download/Install iTunes here
http://www.apple.com/itunes/download.
After that post back and tell me if your songs are listied in iTUnes or if iTUnes is empty