Thanks for all the help, I really really appreciate getting an answer here! 
Of course, unfortunately neither of those worked for me - I’m running Windows XP and did a complete re-install from scratch, as my hard drive had been fried. BUT: In my mad attempts to rescue my files from said drive, I somehow managed to save the complete endnote folder from the programmes section. Found them in a pile of unlabeled, unsorted files that the recovery programme rescued. You can’t believe how relieved I was when I found my style among those files. Best christmas present ever! \o/
So anyway - thank you soooo much for trying to help!
And to all others out there: BACK UP YOUR OUTPUT STYLES!