Default location is C:/Program Files(x86)/PostgreSQL/8.x/data
If you're using a 64 bit version it will be C:/Program Files/PostgreSQL/9.x/data.
Double check if you don't have (a different version of) PostgreSQL installed to a different folder.
If the only folder is C:/postresSQL/data, manually delete the files from the C:/postresSQL/data/pg_log folder.