I occasionally come across other websites that have useful information on the HP t5720 These are collected in this section. If you find others please let me know (use the link at the bottom of the page).
http://qubeserver.com/T5720/Gallery.html
An interesting article in upgrading a t5720 to turn it into a light gaming machine and/or HTPC (Home Theatre PC). Covers upgrading the CPU, adding a fan and graphics card.
https://www.elektroda.pl/rtvforum/topic2206568.html
Something in Polish about fitting a hard disk to a t5720. Lots of photographs
so you don't really have to resort to an on-line translator.
https://www.vogons.org/viewtopic.php?f=46&t=49208
A posting from S0ren on using the t5720 as a gaming machine for old DOS/Windows games such as Duke Nukem 3D. Uses DOS6.0 and Windows 98.
https://gitlab.com/gitendo/t5720"
In November 2023 I heard from 'tmk' who had produced a modified BIOS for the t5720. He describes this as HP T5720 custom BIOS v1.13 with latest VGA ROM and all previously unavailable menu options enabled