faulty modem is killing my laptop

I have an IBM Thinkpad T21 2648-8AU laptop with a broken modem. This modem apparently is causing boot-level, non-controllable and semirepeatable malfunctioning to various linux distros I have installed. It also causes Windows XP installation to hang up in the middle of it. I later sold the laptop and told the buyer about the problem. The problem remains unsolved. To see OS specific error messages,

winXP: installation hangs up during device detection

ubuntu 5.04: after a few (two?) boots upon installation, ubuntu shows the following:

isapnp: No Plug & Play device found
serio: i8042 AUX port at 0x60,0x64 irq 12
serio: i8042 KBD port at 0x60,0x64 irq 1
Serial: 8250/16550 driver $Revision: 1.90 $ 54 ports, IRQ sharing enabled
ACPI: PCI Interrupt Link [LNKC] enabled at IRQ 10
PCI: setting IRQ 10 as level-triggered
ACPI: PCI interrupt 0000:00:03.1[A] -> GSI 10 (level, low) -> IRQ 10
_
(halts at this point)

redhat 9: same as above

isapnp: No Plug & Play device found
Linux NET4.0 for Linux 2.4
Based upon Swansea University Computer Society NET3.039
Initializing RT netlink socket
apm: BIOS version 1.2 Flags 0x03 (Driver version 1.16)
Starting kswapd
VFS: Disk quotas vdquot_6.5.1
pty: 2048 Unix98 ptys configured
Serial driver version 5.05c (2001-07-08) with MANY_PORTS MULTIPORT SHARE_IRQ SERIAL_PCI ISAPNP enabled
PCI: Found IRQ 10 for device 00:03.1
PCI:Sharing IRQ 10 with 00:03.0
Redundant entry in serial pci_table. Please send the output of lspci -vv, this message (115d,000c,8086,2408)
and the manufacturer and name of serial board or modem board
to serial-pci-info@lists.sourceforge.net
_
(halts here)

fedora core 3 used to hang up in the same way. stopped since two weeks ago, apparently. unsure whherein the problem lies.