Hi,
My original problem was that both my laptop speakers and the headphones were playing at the same time when i put in the headphone jack.
I searched for solutions, and this site asked to install realtek drivers for linux. And when I did so, my AlSA doesnt find audio hardware. It shows "Dummy output" in devices list. And no sound comes out.

pratik@Leecher:~$ lshw
WARNING: you should run this program as super-user.
leecher
description: Computer
width: 32 bits
*-core
description: Motherboard
physical id: 0
*-memory
description: System memory
physical id: 0
size: 1019MiB
*-cpu
product: Intel(R) Pentium(R) M processor 2.13GHz
vendor: Intel Corp.
physical id: 1
bus info: cpu@0
version: 6.13.8
size: 800MHz
capacity: 800MHz
width: 32 bits
capabilities: fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov clflush dts acpi mmx fxsr sse sse2 ss tm pbe nx up bts est tm2 cpufreq
*-pci
description: Host bridge
product: Mobile 915GM/PM/GMS/910GML Express Processor to DRAM Controller
vendor: Intel Corporation
physical id: 100
bus info: pci@0000:00:00.0
version: 03
width: 32 bits
clock: 33MHz
configuration: driver=agpgart-intel
resources: irq:0
*-display:0
description: VGA compatible controller
product: Mobile 915GM/GMS/910GML Express Graphics Controller
vendor: Intel Corporation
physical id: 2
bus info: pci@0000:00:02.0
version: 03
width: 32 bits
clock: 33MHz
capabilities: vga_controller bus_master cap_list rom
configuration: driver=i915 latency=0
resources: irq:16 memory:d0600000-d067ffff ioport:3000(size=8) memory:c0000000-cfffffff memory:d0680000-d06bffff
*-display:1 UNCLAIMED
description: Display controller
product: Mobile 915GM/GMS/910GML Express Graphics Controller
vendor: Intel Corporation
physical id: 2.1
bus info: pci@0000:00:02.1
version: 03
width: 32 bits
clock: 33MHz
capabilities: bus_master cap_list
configuration: latency=0
resources: memory:d0700000-d077ffff
*-usb:0
description: USB controller
product: 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB UHCI #1
vendor: Intel Corporation
physical id: 1d
bus info: pci@0000:00:1d.0
version: 03
width: 32 bits
clock: 33MHz
capabilities: uhci bus_master
configuration: driver=uhci_hcd latency=0
resources: irq:19 ioport:3020(size=32)
*-usb:1
description: USB controller
product: 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB2 EHCI Controller
vendor: Intel Corporation
physical id: 1d.7
bus info: pci@0000:00:1d.7
version: 03
width: 32 bits
clock: 33MHz
capabilities: ehci bus_master cap_list
configuration: driver=ehci_hcd latency=0
resources: irq:19 memory:d0780000-d07803ff
*-pci
description: PCI bridge
product: 82801 Mobile PCI Bridge
vendor: Intel Corporation
physical id: 1e
bus info: pci@0000:00:1e.0
version: d3
width: 32 bits
clock: 33MHz
capabilities: pci subtractive_decode bus_master cap_list
resources: ioport:2000(size=4096) memory:d0000000-d05fffff ioport:40000000(size=67108864)
*-network:0
description: Wireless interface
product: PRO/Wireless 2200BG [Calexico2] Network Connection
vendor: Intel Corporation
physical id: 4
bus info: pci@0000:02:04.0
logical name: eth1
version: 05
serial: 00:16:6f:c1:cd:da
width: 32 bits
clock: 33MHz
capabilities: bus_master cap_list ethernet physical wireless
configuration: broadcast=yes driver=ipw2200 driverversion=1.2.2kmprq firmware=ABG:9.0.5.27 (Dec 12 2007) ip=192.168.11.2 latency=64 maxlatency=24 mingnt=3 multicast=yes wireless=IEEE 802.11bg
resources: irq:21 memory:d0000000-d0000fff
*-pcmcia
description: CardBus bridge
product: CB1410 Cardbus Controller
vendor: ENE Technology Inc
physical id: 6
bus info: pci@0000:02:06.0
version: 01
width: 32 bits
clock: 33MHz
capabilities: pcmcia bus_master cap_list
configuration: driver=yenta_cardbus latency=176 maxlatency=5 mingnt=192
resources: irq:18 memory:d0001000-d0001fff ioport:2400(size=256) ioport:2800(size=256) memory:40000000-43ffffff memory:44000000-47ffffff
*-network:1
description: Ethernet interface
product: PRO/100 VE Network Connection
vendor: Intel Corporation
physical id: 8
bus info: pci@0000:02:08.0
logical name: eth0
version: 03
serial: 00:16:d4:eb:ba:f3
size: 10Mbit/s
capacity: 100Mbit/s
width: 32 bits
clock: 33MHz
capabilities: bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation
configuration: autonegotiation=on broadcast=yes driver=e100 driverversion=3.5.24-k2-NAPI duplex=half latency=64 maxlatency=56 mingnt=8 multicast=yes port=MII speed=10Mbit/s
resources: irq:20 memory:d0002000-d0002fff ioport:2000(size=64)
*-multimedia UNCLAIMED
description: Multimedia audio controller
product: 82801FB/FBM/FR/FW/FRW (ICH6 Family) AC'97 Audio Controller
vendor: Intel Corporation
physical id: 1e.2
bus info: pci@0000:00:1e.2
version: 03
width: 32 bits
clock: 33MHz
capabilities: bus_master cap_list
configuration: latency=0
resources: ioport:3100(size=256) ioport:3200(size=64) memory:d0781000-d07811ff memory:d0782000-d07820ff
*-communication UNCLAIMED
description: Modem
product: 82801FB/FBM/FR/FW/FRW (ICH6 Family) AC'97 Modem Controller
vendor: Intel Corporation
physical id: 1e.3
bus info: pci@0000:00:1e.3
version: 03
width: 32 bits
clock: 33MHz
capabilities: generic cap_list
configuration: latency=0
resources: ioport:3400(size=256) ioport:3500(size=128)
*-isa
description: ISA bridge
product: 82801FBM (ICH6M) LPC Interface Bridge
vendor: Intel Corporation
physical id: 1f
bus info: pci@0000:00:1f.0
version: 03
width: 32 bits
clock: 33MHz
capabilities: isa bus_master
configuration: latency=0
*-ide
description: IDE interface
product: 82801FB/FBM/FR/FW/FRW (ICH6 Family) IDE Controller
vendor: Intel Corporation
physical id: 1f.1
bus info: pci@0000:00:1f.1
version: 03
width: 32 bits
clock: 33MHz
capabilities: ide bus_master
configuration: driver=ata_piix latency=0
resources: irq:16 ioport:1f0(size=8) ioport:3f6 ioport:170(size=8) ioport:376 ioport:3580(size=16)
WARNING: output may be incomplete or inaccurate, you should run this program as super-user.
pratik@Leecher:~$
And I could not find alsamixer (sudo doesn't work either!)
pratik@Leecher:~$ alsamixer
cannot open mixer: No such file or directory
pratik@Leecher:~$ sudo alsamixer
cannot open mixer: No such file or directory
pratik@Leecher:~$
Therefore, now, no audio comes out!
May be uninstalling the realtek driver could help...