If you don’t have a lot of installed software, and/or if what you do have is from the store, or maybe Microsoft 365, you can probably get away with never backing up your Windows PC &/or laptop – worse case, after a hard disk failure you reinstall everything to a new hard disk. For some people however, surviving the loss of a hard disk without a backup can seem pretty close to impossible -- I’ve got several Corel apps that are not available to download for example – you get a link that’s good for a couple of months when you buy the software, and after that you’re out of luck. O&O DiskImage is a potential solution, though it doesn’t match Paragon’s HDM or Macrium Reflect. DiskGenius is another, similar app you might look at, with free & portable versions, but a GUI that seems to me designed to confuse. Till the 26th O&O has a coupon code -- HOLIDAYS22 -- if anyone's interested.
O&O has been at it a long time – *IF* I remember correctly, their backup software used to be a bit *different* from everybody else. That history shows a little bit as DiskImage 18 offers to create a partition to hold your backup archives, seems like it wants you to add DiskImage to your boot menu, never calls their rescue media, rescue media, and offers to add boot files when/if you backup a disk / partition that does not include them. The main purpose of the app, backing up & restoring disk / partition images works, though it’s not as fast as Macrium Reflect, which can bypass Windows to a great extent reading & writing to hard disks / SSDs. However, when that’s not in use, e.g., writing to a mounted VHD [Virtual Hard Disk], O&O DiskImage is actually a little faster. That said, in testing DiskImage presented me with a dialog box asking if I wanted to restore a backup using file copy or sector by sector – when I chose the file option DiskImage crashed, twice, with a notification its service wasn’t running.
One thing that DiskImage cannot do that Paragon HDM and Macrium Reflect handle quite nicely, is restore an image backup to a target that has less space than the original source. The workaround isn’t too bad, though it’s still a workaround… An image backup program clones a disk / partition, copying the raw data to an archive. That archive is usually a VHD so that it can be mounted, giving you access to individual files/folders. DiskImage lets you choose the format of that archive, letting you select the app’s native format, or .vhd or .vhdx – the latter two can natively be mounted in Windows at Control Panel -> Admin Tools -> Computer Management -> Disk Management. [Windows 11 calls it Windows tools instead of Admin Tools.] So, if you backup a disk / partition, saving it as a .vhd or .vhdx file, you can mount that file in Windows, & it’ll behave just like a hard disk partition. And one of the easiest things you can do to a partition is shrink its total size.
*As long as the data on the original partition does not take up more space than is available on the target*, you can mount your backup .vhd or .vhdx file, you can defrag [optimize] that VHD, packing all the data to the front, & then you can use any number of tools, e.g., AOMEI Partition Assistant [a free version's available], to shrink that partition down to the size you need to fit. Then, once you dismount that VHD, DiskImage can restore it in that smaller space. Note: it can be hard to get partition sizes exact, but if you size the VHD’s partition a little smaller than necessary, it’s easy to enlarge that partition once it's restored – just use the same tool you used to shrink it. It sounds like more work than it is – in testing it took just 2 or 3 minutes plus the defrag to mount the VHD & shrink the partition.
If you can’t start Windows, you can’t use backup software to restore a backup, or to copy those files to a replacement hard disk / SSD if the one you were using fails – you need to run that software in another, working copy of Windows. As far as I know every brand of image backup software has a tool to create a USB stick that will boot your PC / laptop & run a copy of that backup software so that you can restore a backup image. Many brands of backup software, however, cannot create a USB stick that boots [starts] a current PC or laptop using UEFI BIOS and Secure Boot, e.g., AOMEI, EaseUS, MiniTool etc. The USB stick you can create with DiskImage does work, but the built-in tool to create it Needs Work…
To start with, when you open the tool, it will ideally show that it can use the recovery image [.wim file] that Windows adds to its recovery partition when Windows is installed. In a Windows 10 and a Windows 11 VM [Virtual Machine], in 2 copies of Windows 11, and in one copy of Windows 10, DiskImage failed to see that recovery image, even though competing brands of backup software had no trouble finding & using them. Next, you need to click the 2nd tab in the window, OO DiskImage ToGo, to be able to select a USB stick – that wasn’t clear to me at first. Then once you select a plugged in USB stick you cross your fingers and click the Create button. First try it destroyed the USB stick. 2nd try the tool stalled when it finished, so I had to close DiskImage using Task Mgr. It refused to work with an SSD in an external USB housing, but, once I got a working USB stick I copied all the files & folders over to that SSD & it works fine.