Let's start with some definitions.
- UEFI is the successor to the more traditional BIOS. The implementations vary but they all offer a BIOS compatibility mode (may be disabled by default).
- GPT is the successor to the traditional DOS partition table that offers a number of benefits notably support for booting from drives >= 2TB and >4 partitions without using a "hackish" extended partition.
- UEFI/GPT boot standard utilizes a FAT32 "ESP" partition to contain the relevant bootloader files.
- BIOS/DOS boot standard writes the bootloader within the first 512 bytes (MBR) which often chainloads configuration files from a partition.
As you mentioned laptops and the maximum capacity for 2.5" drives is 1TB currently and your priority appears to be maximizing compatibility, a traditional BIOS/DOS/MBR is recommended.
You may utilize gdisk
or another tool for the conversion (though loss of data is high for such a task) and then install GRUB bootloader to the MBR. You may need to enable BIOS-compatibility mode in the UEFI settings to boot.
Squircle's answer and various comments are good; however, I want to address a few points....
I don't have the CSM mode option in my UEFI. Furthermore, I can't and don't want to convert my hard drive form MBR to GPT
It is possible to convert from MBR to GPT without losing data. My own GPT fdisk (gdisk
) program can do this. I hear that some third-party Windows tools can do it, too, but I don't know the details. Microsoft's own tools cannot do this, though, so do not try to use them for the task. Note that MBR-to-GPT conversion is very simple compared to something like converting from one filesystem to another, so the risk is low -- but not zero. No operation that involves writing to data structures as sensitive as a partition table is zero-risk.
You say you "don't want" to convert to GPT, but you don't say why. If it's simply the hassle or risk of conversion, that's dwarfed by follow-on problems of the near-complete lack of support you'll face by using MBR. (I am, however, assuming that you have or can create adequate backups. If that's incorrect, FIX THAT PROBLEM IMMEDIATELY! Backups are NOT a luxury!) If, like some people, you're comfortable with MBR and just don't see a need to change to some [crotchety old-man voice]new-fangled thingamajig[/crotchty old-man voice], then I recommend you shed your biases. GPT offers real advantages over MBR. Most of them are minor, but if you must boot in EFI mode, the fact that GPT is the standard for EFI-mode booting is not a minor advantage; it's a major one.
Windows (uniquely) requires GPT to use EFI
My understanding is that this is a requirement of the Windows installer, but it's possible to get Windows to boot in EFI mode from an MBR disk by using various tricks, like converting from GPT to MBR after installing the OS, or by replacing a BIOS-mode boot loader with an EFI-mode boot loader without changing the partition table type. That said, my knowledge of precisely how best to achieve this goal is foggy, since I've only read about it; I've never done it myself. I've read about this only once or twice in several years, so this is not something that's done very often.
Can the EFI system partition be a logical partition ?
In theory, it shouldn't matter. In practice, I don't know. Booting in EFI mode from an MBR disk is such a corner case that there's a small but non-negligible chance that literally nobody in the world has tried using an MBR logical partition as an ESP. Certainly I haven't tried it. Please keep this in mind if you decide to pursue booting in EFI mode from an MBR disk -- your odds of getting expert (or even advanced amateur) help drop to near zero should you run into problems.
Overall, my recommendation is to look into MBR-to-GPT conversion tools. Chances are you'll be able to convert from MBR to GPT without trouble. The result will be less likely to cause problems than trying to boot in EFI mode from an MBR disk. You should, however, back up before doing this. That would be my advice even without an MBR-to-GPT conversion in the picture, though; mucking with boot loaders can be as risky as mucking with partition tables, so trying that without a backup is inadvisable, too.
Best Answer
You're not asking about safety, but about support. Yes, EFI firmware has no trouble with an MBR partition table, which it can cope with just as it can cope with an EFI partition table. You just need to make sure that you have an EFI System Partition.
Your problem is Windows. Microsoft erroneously conflates has a GPT partitioned disc with bootstraps in the EFI way. So your laptop with a modern EFI partition table and modern EFI firmware has been installed and is bootstrapping Windows in the modern EFI way. Change to an MBR style partition table, and Windows will expect to be bootstrapping in the old PC98 way. You'd have to switch on the Compatibility Support Module option in your firmware, if it has it, and either reinstall Windows or individually modify the Microsoft Boot Manager, the system BCD store, the system volume's VBR, and the MBR bootstrap program.
All that fuss, and a massive step backwards, just for a rather dodgy "boot logo changer" and a "Microsoft Toolkit" that's almost certainly not Microsoft's? (Some quick searches turned up various things purporting to be these. Perhaps the most appalling was the one that gave step by step instructions to the marks for turning off security, patching their system files to turn off warnings of danger, and trusting a new root certificate; roping them in with the promise of a different picture at bootstrap time. But the bogus "anti-virus" company falsely telling people that Microsoft wrote AutoKMS so they shouldn't worry their pretty little heads about it came a close second.) I suggest not.