I'm not sure what means that HWiNFO didn't work, but I assume the suggested boot CD loads too many drivers/programs so there's not much free memory available for HWiNFO. In that case please refer to this post for more information: <!-- l --><a class="postlink-local" href="http://www.hwinfo.com/forum/viewtopic.php?f=6&t=23">viewtopic.php?f=6&t=23</a><!-- l -->
Also, maybe it would be better and easier to create a DOS bootable USB key (in case the BIOS supports bootable USB media).
Martin you are probably have own boot image with DOS HWiNFO perhaps you can give, I'll take a look.
I'm usually using a DOS-bootable USB key with plain MS-DOS 5.0 (or 6.2) with only the most important devices loaded as described in the post earlier (HIMEM.SYS).
The tool I used to create a DOS bootable USB key is called:
HP Windows Format Utility for USB Drive Key or DiskOnKey