grabit and disk space help

hi,
can anyone please help me out with grabit i have grabit install on my 40 GB internal hard drive on my computer but the download folder is set to my 320 GB external hard drive i had 21 GB of free space on my internal hard drive on my computer and now that i have install grabit on my computer i have lost 12 GB of that 21GB that i had on my computer i have tryed removing grabit from my computer but still cant get back that the 12 GB that i have lost i dont know if it becaues of the cache folder or were to find the cache folder if its the cache folder