I have a Series3 HD TiVo (TCD652160). I have upgraded the original 160GB Hard Drive to a 500GB using 'winmfs' Mfscopy. No problems I verified in the system settings that it stated I had up to 75 HD hours. It has now been a couple of months and I started running out of space to record. I checked back in the system settings and now it states that I only have 21 HD hours. I restarted the Tivo and it still says the same. Does the model of the Tivo reset this or could it be a software upgrade? Software Version is: 11.Ok-01-2-652 Any ideas?