MacFixIt Answers is a feature in which we answer e-mailed questions from our readers. This week we have questions about a Mac not booting after months of no use, heat differences between the 15-inch and 17-inch MacBook Pro, upgrading a commercial external hard drive, bootable backup options, and the difference between partitioning and using two drives. We continually answer e-mail questions, and though we present a few answers here, we certainly welcome alternative approaches and views from readers and encourage you to post your suggestions in the comments.
Question: Mac not booting after months of no use
MacFixIt reader "Sashi" asks:
When I switch on my 24-inch imac after an absence of two or three months, it does not boot. Apple icon is seen but the screen is as good as frozen. I have to reinstall operating system and as a result I loose all my files. Please advise how to prevent this.
You might not need to perform a full reinstallation and lose your files. Try booting to the OS X installation disk and then use Disk Utility (from the Utilities menu in the installer--available after you select your language) to repair the boot drive. In addition, try booting into Safe Mode by holding the Shift key during start-up. This may allow the system to boot properly.
If you are able to use these methods to boot the system, be sure to first back up all your important files and then consider addressing the problem in more depth. For instance, if you can only boot into Safe Mode or if the system seems to crash often or run slowly, you might consider formatting and reinstalling the OS. You can also try running aon the system to see if that clears up some small slowdowns.
Question: Heat differences between 15-inch and 17-inch MacBook Pros
MacFixIt reader "Jayme" asks:
Just wondering if the 17-inch has bigger fans and heat sync compared to the 15-inch which could lead to a cooler running machine. I ask as I saw amazing temps with the new 17-inch [in the] store but they didn't have a 15-inch which is what I would prefer.
The logic boards, processors, and fans used in the two systems are relatively similar, and the logic board size is roughly the same. The older MacBook Pro that used dual Nvidia chipsets had a heat-sink extender that covered the logic board controller, but the newer machines that use the Intel controller do not have this extender.
One possible reason why there's a heat difference could be the overall size of the machine, and heat dissipation through the chassis (which is used in part to dissipate heat). Another reason could be differences in the chips used. Some machines might have the Core i5 whereas others might have the Core i7, and they also might be at different clock speeds.
Question: Upgrading a commercial external hard drive
MacFixIt reader "braceemup" asks:
Has anyone replaced an old 40GB HD from a SmartDisk Firelite with a larger one? I just recently replaced my MBP HD 320GB with a Seagate 750GB. I would like to place the removed 320GB HD into an old Firelite case, but would like to know of anyone's experience attempting this. I am not sure if the HD in the Firelite is a 2.5" and if so if the connections will be compatible.
I have not done this with this model specifically, but have done it with other drives with no problem at all. Most external drives contain a simple controller and firmware that should interface with similar hard drives out there, without any issues. Therefore if you are able to get the drive open you should be able to replace the drive with no problem. The only problems might be if the enclosure's firmware is coded to only use a specific hard-drive make or model (highly unlikely) or if there is a mechanical block or temperature issue. Hard drives can get hot, and if the newer drive gets hotter than the current one then you might chance overheating the thing; however, this can usually be gauged by feel.
Question: Bootable backup options
MacFixIt reader "Roger" asks:
Is there a way to make a bootable backup of only the system and users files? I would like to do this on an external drive, to make repairs on the internal hard drive.
This can be done with any "cloning" utility. Some notable ones are Carbon Copy Cloner, SuperDuper, Drive Genius, and even Disk Utility. See for more information on cloning your hard drive.
Question: Partitioning versus using two hard drives
MacFixIt reader "Leslie" asks:
Isn't partioning the same internal 3TB into two 1.5TB the same as two external drives?
It is technically not, though for most intents and purposes they will be the same thing.
Partitioning a drive is taking a single physical drive and slicing it into two "logical" volumes, which is similar to attaching two drives to the Mac, except that both volumes are on one drive instead of two. This makes transfer between the volumes and accessing them faster, but in the event of a drive failure or partition table corruption you chance losing all the partitions (each volume). With two external drives the volumes are independent so if one fails the other will be fine, but they will be on slower USB/FireWire connections and also might require additional power. Additionally, with external drives there is more chance of odd mishaps (such as power failures and connection interruptions) that could impact performance and stability.