>When I reboot my XP, my NT4.0 drives disconnect??

Have you checked your NT login script to see if it is clearing shares before it attempts to assign its own? A sample login script for one of my users looks like:

@ECHO OFF
REM SBT\OE\DOM Server drives
rem map delete f:
rem net use f: /D
rem net use g: /D
rem net use i: /D
rem net use p: /D
rem net use w: /d
rem net use x: /d
rem net use y: /d
rem net use o: /D

Rem the lines above disconnected drives prior to their being remapped

net use f: \\xxxxxxxxxx\xxxxxxxxxxx /yes /persistent:yes
net use g: \\xxxxxxxxxx\xxxxxxxxxxx /yes /persistent:yes
net use i: \\xxxxxxxxxx\xxxxxxxxxxx /yes /persistent:yes
cd f:\xxxxx
cd g:\xxx
cd i:\xxxxx
net use y: \\xxxxxxxxxx\xxxxxxxxxxx /yes /persistent:yes
net use w: \\xxxxxxxxxx\xxxxxxxxxxx /yes /persistent:yes
net use x: \\xxxxxxxxxx\xxxxxxxxxxx /yes /persistent:yes
net use o: \\xxxxxxxxxx\xxxxxxx /yes /persistent:yes
cd y:\xxxxx
cd x:\xxxxx
cd w:\xxxxxxxx
cd o:\xxxx
REM VAM Mapping
net use p: /D
net use p: \\xxxxxxxxxx\xxxxxxxxxxxx /yes /persistent:yes
cd p:\xxx
REM Printer mappings
IF *%LOCALPTR%*==*1* GOTO CHECK2
NET USE LPT1 /D
NET USE LPT1 \\xxxxxxxxxx\xxxxxxx /yes /persistent:yes
:CHECK2
NET USE LPT2 /D
IF *%USERNAME%*==*xxxxxx* GOTO DOLPT2
IF *%USERNAME%*==*xxx* GOTO DOLPT2
ECHO Co 10 Invoices go to Delores
NET USE LPT2 \\xxxxxxxxxx\xxxxxxx /yes /persistent:yes
GOTO DOLPT3
:DOLPT2
ECHO Checks go to the Check bin in Marty's office
NET USE LPT2 \\xxxxxxxxxx\xxxxxx /yes /persistent:yes
:DOLPT3
NET USE LPT3 /D
NET USE LPT3 \\xxxxxxxxxx\xxxx /yes /persistent:yes
:EXITPT
NET USE LPT4 /D
NET USE LPT4 \\xxxxxxxxxx\xxxxxxx /yes /persistent:yes

As you can see, we delete pre-existing mappings for both drives and printers to reassign them safely; you might be encountering the same thing.