Yes, I realised that after posting. I used Media Creation Tool to make a 32 bit Win 10 dvd, but before I could use it I wanted to sort out the boot problem I've had since trying the VHD. I eventually figured it out - following the Test & Try tutorial I had used the bcd command to tell the PC to boot into the virtual machine. I re-installed EasyBCD, which I used four years ago to set up my dual boot in the first place, and removed Windows 10 from the boot list. So my system was basically back how it started.

When I tried booting with the 32 bit dvd in the drive, the pc ignored it and went straight to the dual boot menu. I think it's because an external usb drive. So I used Media Creation Tool again to make a 32 bit Win 10 usb. Every time I use the tool it downloads another copy of Windows, so everything takes much longer than necessary. Anyway, booting with this new usb, I get back to the old four rectangles logo screen...

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I'm going to mark this as solved. My problem isn't exactly solved, but you've all helped me reach the conclusion that my PC's conclusion can't handle Windows 10. I'm sticking with Win 7 until I can upgrade. I've thanked you all.