I'll probably be flamed for this but I'd recommend the HP, even over an IBM. I recently bought a Compaq X1000 (I think it's the Compaq version of the ZT3000) and I'm EXTREMELY impressed with it. I only bought it because it was a hot deal. I didn't expect to keep it but I was happily surprised. I actually like it a good bit more than my IBM T40. The only big thing the IBM has over it is smaller size. Everything else seems better about the Compaq. The major thing I like about the Compaq is the entire video system is drastically better. The IBM has a Radeon 9000 32MB and the Compaq has a Radeon 9200 64MB. The Compaq runs thing noticably faster.
My other big (the biggest in fact) problem with the IBM is the LCD. It's 14.1" SXGA+ LCD is one of the worst I've seen recently. The contrast/brightness is just pitiful and it has horrible ghosting. I also noticed that the refresh rate is only 50Hz. In contrast the Compaq has a beautiful 15.4" WXGA LCD. The contrast/brightness is very good and there is very little ghosting. It's not the best LCD I've seen (that would be the Samsung 152T) but it is the best LCD I've seen on a laptop. BTW, I don't particularly like the wide aspect ratio but I can live with it.
Overall the T40 and X1000 are both excellent laptops but I personally like the X1000 better. I don't know about the Dell Inspiron 86000 but I did have an Inspiron 8200 and it had some major flaws but they may have been fixed since. Just a few other notes. The battery life on the Compaq is amazing. It ran for about 3:30 with the LCD at full brightness (compared to 2:45 for the IBM). Also the fan runs VERY little on the Compaq. It's not as cool as the IBM but it's much cooler than my old Inspiron 8200. The great thing is it basically never comes on under normal use (web surfing, etc.). It only comes on when running games, etc. I hope this helps.