Problem with downloading from TopSony

Hello there...

I would like to full flash my old k770i (i have read aaaall the tutorials etc - im still confused on how - my english is not so good plus the fact Im new in forums and in cellphone language and term)
I understood that I have to download the correct firmware, SF and custompack but I dont know where to find Sf and how to use the custompack.

( I took from xs++ these details:

04:07:11| Profiling SEMC phone...
04:07:11| Platform: DB2020
04:07:11| OTP CID: 51
04:07:11| EROM CID: 52
04:07:11| EROM Color: Red
04:07:11| IMEI: 35852401xxxxxx
04:07:11| Phone ID: K770
04:07:11| Region: VFE_LIVE_1
04:07:11| CDA: 1202-4266 R4A
04:07:11| Firmware Version: R8AC001
04:07:11| EROM: R3A022
04:07:11| Ready for operation! )

I would like to flash my phone in CDA 1210-7539 MEDITERR (Cosmote Greece and leave vodafone menus and all behind).....

But Im offtopic... the reason im posting is because the firmware i tryied to download (K770_R8BA024_FS_MEDITERR_RED52) , after it's finished, it cant be extracted.. I get this mesage from winrar: "The file is corrupt" and "unexpected end of archive"...

Im almost sure that i have the wrong firmware (and any help on this would be good) but my main problem is that I cant even try to flash my phone with the wrong firmware!!

Thank you in advance,
im greatfull for any tip that could help me...