It is a known problem (according to a guy who contacted nVidia) of GF3 and some GF2 cards. GF4 don't have it. All drivers above 40.72 seem to hang the boot process. Actualy, it doesn't hang, you have to wait for about 2 minutes more and Windows will load eventually. The only cure is to go back to 40.72 and wait for the new drivers nVidia is working on.
I have the same problem, and it also started because of Unreal 2 :D I tried all kinds of versions, betas and all, but it's always the same story - my PC boots 2 minutes longer (3 minutes in total), but when it loads, everything is ok, Unreal 2 works fine, no BSODs (although many users reported having frequent BSODs and stability issues also), and so on.
Actually, nVidia's 41.09 created some serious slowdowns on my system, but MSI's 41.07 work just fine, except for that 3 minutes boot process (which is quite irritating).
I will finish Unreal 2 and then install 40.72 and wait for new detonators from nVidia.... (sigh) :(
My system: Asus A7V133, VIA KT133A, XP 1800+, MSI GF3Ti200 64DDR, SB Live! 1024, 512 SDRAM, 30 GB U-ATA 100, network and ISDN PCI cards, Windows Millenium, dx 8.1.
For more info go to Detonator forum on http://www.guru3d.com
, there is a thread about it.