I had that warrenty sticker thing a few years ago.
It was a pentium 166 i had bought for £1800 with 32mb ram
.I had bought another 32mb ram and rang them up about it,at first they said it would void the warrenty until i said ok then i'll send it back post paid by you and you fit the ram and post it back at your expense.They relented and said it would'nt void the warrenty if i fitted the ram.