dhcp prob w/ xp home

[Robpol86]

I work @ Tisd.net (a 56k ISP) as customer support
theres this computer here that im workin on to fix a prob related to the internet
when it dials up, it connects successfully and the 2 computers r in the tray.
but when i try to use it (ie, ping, outlook express, etc.) it wont work. i checked ipconfig and it gave me sum weird info.
first, the ip is awkward. the isp uses a class C ip and the computer is assigned a class A ip (dunno the #s) but my supervisor told me that they auso use those class A ips but rarly. no1 uses them except this comp. it also gives me a different subnet mask. instead of 255.255.255.0 its 255.255.255.255

also, when i do ipconfig /all, it tells me
DHCP Enabled.............. :No

even though it uses "obtain ip address automatically" in the tcp/ip props. i tried disabling compression, diff telephone #'s but nothin will work. i tried static ip but i dont like playing the guessing game....

ne1 know how 2 "enable" dhcp in xp home?



edit:
when i plugged it in the company lan, it gave me sum more weird stuff.
now it said dhcp was enabled but the ip address was 169.??? (dunno the entire ip, 2 lazy) and its suppose 2 b 192.168. it also gave me a subnet if 255.255.0.0
this is the most f'ed up computer ive seen...