Main Index Pablo Honey The Bends OK Computer Kid A Amnesiac Hail to the Thief In Rainbows The King of Limbs A Moon Shaped Pool Thom Yorke Jonny Greenwood Ed O'Brien Colin Greenwood Philip Selway Music Video
The song was played on a number of shows in 1996, this recording (from 'MiniDiscs [HACKED]') is from March 27th at The Fillmore in San Francisco, and was the first live appearance of the song:
The band also performed 'I Promise' during the august 1996 US dates, when they played in support of Alanis Morissette. This video comes from august 14th 1996:
To this day, this version from August 27th 1996 in Pittsburgh (also from 'MiniDiscs [HACKED]') is the last known public performance of 'I Promise':
Radiohead recorded 'I Promise' during the OK Computer sessions. This version, that according to Thom sounds a bit like Joy Division, has been released in 2017 on the OKNOTOK 20th anniversary edition of OK Computer.
The latest available recording of this song is a soundcheck from september 8th 1997:
Ed stated in november 1998 that this song might be recorded for what turned out to be Kid A and Amnesiac:
Speaking of new songs, guitarist Ed O'Brien confided to reporters this fall that 'I Promise', and 'True Love Waits', two of their unreleased songs that the band routinely play for sound checks, and 'Motion Picture Soundtrack', which has appeared as a final encore in the past, could end up on the new album. Furthermore, O'Brien told NME that the band had already worked on some stuff in the back of their tour bus while they were on the road for the last album.
However, it's not known if they attempted it at all, and it is isn't mentioned anywhere in Ed's online diary.
Pages relating to this song can be found in the books that were published in the OKNOTOK deluxe box set (click to view the full image):

'I Promise' was released as part of the OKNOTOK 20th anniversary edition of OK Computer and subsequently played live three times:
  2017 A Moon Shaped Pool tour march/april 2017 june 2017 july 2017
I Promise [3] 07 20 04