Pentium M processor, PAE (Physical Address Extension) not reported as one of the CPU's features, so it is consequently unable to install latest Trisquel (6, currently.) Here is a way to install Trisquel on this computer, bypassing the artificial install restriction.

2 GB maximum RAM.

lspci -v:

00:00.0 Host bridge: Intel Corporation 82855PM Processor to I/O Controller (rev 03)
	Flags: bus master, fast devsel, latency 0
	Memory at e0000000 (32-bit, prefetchable) [size=128M]
	Capabilities: <access denied>

00:01.0 PCI bridge: Intel Corporation 82855PM Processor to AGP Controller (rev 03) (prog-if 00 [Normal decode])
	Flags: bus master, 66MHz, fast devsel, latency 32
	Bus: primary=00, secondary=01, subordinate=01, sec-latency=32
	I/O behind bridge: 0000c000-0000cfff
	Memory behind bridge: fc000000-fdffffff
	Prefetchable memory behind bridge: e8000000-efffffff

00:1d.0 USB Controller: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #1 (rev 01) (prog-if 00 [UHCI])
	Subsystem: Intel Corporation Latitude D400
	Flags: bus master, medium devsel, latency 0, IRQ 11
	I/O ports at bf80 [size=32]

00:1d.1 USB Controller: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #2 (rev 01) (prog-if 00 [UHCI])
	Subsystem: Intel Corporation Latitude D400
	Flags: bus master, medium devsel, latency 0, IRQ 11
	I/O ports at bf40 [size=32]

00:1d.2 USB Controller: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #3 (rev 01) (prog-if 00 [UHCI])
	Subsystem: Intel Corporation Latitude D400
	Flags: bus master, medium devsel, latency 0, IRQ 11
	I/O ports at bf20 [size=32]

00:1d.7 USB Controller: Intel Corporation 82801DB/DBM (ICH4/ICH4-M) USB2 EHCI Controller (rev 01) (prog-if 20 [EHCI])
	Subsystem: Dell Latitude D600
	Flags: bus master, medium devsel, latency 0, IRQ 11
	Memory at f4fffc00 (32-bit, non-prefetchable) [size=1K]
	Capabilities: <access denied>

00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev 81) (prog-if 00 [Normal decode])
	Flags: bus master, fast devsel, latency 0
	Bus: primary=00, secondary=02, subordinate=0a, sec-latency=32
	I/O behind bridge: 0000d000-0000efff
	Memory behind bridge: f6000000-fbffffff

00:1f.0 ISA bridge: Intel Corporation 82801DBM (ICH4-M) LPC Interface Bridge (rev 01)
	Flags: bus master, medium devsel, latency 0

00:1f.1 IDE interface: Intel Corporation 82801DBM (ICH4-M) IDE Controller (rev 01) (prog-if 8a [Master SecP PriP])
	Subsystem: Intel Corporation Latitude D400
	Flags: bus master, medium devsel, latency 0, IRQ 11
	I/O ports at 01f0 [size=8]
	I/O ports at 03f4 [size=1]
	I/O ports at 0170 [size=8]
	I/O ports at 0374 [size=1]
	I/O ports at bfa0 [size=16]
	Memory at 30000000 (32-bit, non-prefetchable) [size=1K]

00:1f.5 Multimedia audio controller: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) AC'97 Audio Controller (rev 01)
	Subsystem: Dell Unknown device 011d
	Flags: bus master, medium devsel, latency 0, IRQ 5
	I/O ports at b800 [size=256]
	I/O ports at bc40 [size=64]
	Memory at f4fff800 (32-bit, non-prefetchable) [size=512]
	Memory at f4fff400 (32-bit, non-prefetchable) [size=256]
	Capabilities: <access denied>

00:1f.6 Modem: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) AC'97 Modem Controller (rev 01) (prog-if 00 [Generic])
	Subsystem: Conexant D480 MDC V.9x Modem
	Flags: medium devsel, IRQ 5
	I/O ports at b400 [size=256]
	I/O ports at b080 [size=128]
	Capabilities: <access denied>

01:00.0 VGA compatible controller: ATI Technologies Inc Radeon RV250 [Mobility FireGL 9000] (rev 02) (prog-if 00 [VGA controller])
	Subsystem: Dell Unknown device 011d
	Flags: bus master, VGA palette snoop, stepping, 66MHz, medium devsel, latency 32, IRQ 11
	Memory at e8000000 (32-bit, prefetchable) [size=128M]
	I/O ports at c000 [size=256]
	Memory at fcff0000 (32-bit, non-prefetchable) [size=64K]
	[virtual] Expansion ROM at fc000000 [disabled] [size=128K]
	Capabilities: <access denied>

02:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5705M Gigabit Ethernet (rev 01)
	Subsystem: Dell Latitude D400
	Flags: bus master, 66MHz, medium devsel, latency 32, IRQ 11
	Memory at faff0000 (64-bit, non-prefetchable) [size=64K]
	Capabilities: <access denied>

02:01.0 CardBus bridge: O2 Micro, Inc. OZ711EC1 SmartCardBus Controller (rev 20)
	Subsystem: Dell Unknown device 011d
	Flags: bus master, stepping, slow devsel, latency 168, IRQ 11
	Memory at f6000000 (32-bit, non-prefetchable) [size=4K]
	Bus: primary=02, secondary=03, subordinate=06, sec-latency=176
	Memory window 0: 34000000-37fff000 (prefetchable)
	Memory window 1: 38000000-3bfff000
	I/O window 0: 0000d000-0000d0ff
	I/O window 1: 0000d400-0000d4ff
	16-bit legacy interface ports at 0001

02:01.1 CardBus bridge: O2 Micro, Inc. OZ711EC1 SmartCardBus Controller (rev 20)
	Subsystem: Dell Unknown device 011d
	Flags: bus master, stepping, slow devsel, latency 168, IRQ 11
	Memory at f6001000 (32-bit, non-prefetchable) [size=4K]
	Bus: primary=02, secondary=07, subordinate=0a, sec-latency=176
	Memory window 0: 3c000000-3ffff000 (prefetchable)
	Memory window 1: 40000000-43fff000
	I/O window 0: 0000d800-0000d8ff
	I/O window 1: 0000dc00-0000dcff
	16-bit legacy interface ports at 0001

02:03.0 Network controller: Broadcom Corporation BCM4306 802.11b/g Wireless LAN Controller (rev 03)
	Subsystem: Dell Wireless 1350 WLAN Mini-PCI Card
	Flags: bus master, fast devsel, latency 32, IRQ 5
	Memory at fafee000 (32-bit, non-prefetchable) [size=8K]