USB not decting plug n play devices

You can get all the specs from here: Compaq Presario SR1810NX Desktop PC Product Specifications

did you use the troubleshooter and updated the driver as mentioned in the following link?
http://windows.microsoft.com/en-US/windows/help/no-sound-in-windows

The mother board will support any Socket 939 AMD Athlon X2 Processor upto the 4800+ model.

However Socket 939 Processors were discontinued so you may have a hard time finding a "New" one.

Bad Power Supply. Weak Voltage power rail.

Not enough power to turn the Processor on, and keep it on.

1) ALL those LED lights together, use less than 1 Watt of power.

2) EACH fan uses 2 to 3 Watts

3) A typical Processor can use 51 to 125 Watts. Depends on what Processor it is. (Older Processors use less Wattage)

The Compaq Presario SR1810NX desktop computer, comes with an AMD Sempron 3200+, processor.

(Uses the Socket 939 processor socket)

[Maximum operating capability is a 1.8GigaHertz frequency rate.
1.8GHz

Giga = Approximately 1 Billion
Hertz stands for Cycles per Second.
Frequency Rate is correct computer speak for 'Speed'
The AMD Sempron 3200+ processor, can operate at a maximum frequency rate of 1.8 Billion Cycles per Second ]

HP Support >Compaq Presario SR1810NX desktop computer > Product Information > Product Specifications,

http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00609384&tmp_task=prodinfoCategory&lc=en&dlc=en&cc=us&product=1841795&lang=en

The AMD Sempron 3200+, can use up to 62 Watts,

http://en.wikipedia.org/wiki/List_of_AMD_Sempron_microprocessors#.22Palermo.22_.28Socket_939.2C_E3_.26_E6.2C_90_nm.29

(Palermo Core)

When you press the plastic Power On button, you are contacting a Power On switch inside it.
(Typical ATX Power On switch,

http://www.directron.com/atxswitch.html )

When an ATX power supply is plugged into power, there is a 5 Volt Standby power, present inside the power supply.

Pressing the momentary contact power on switch, closes a circuit that directs the 5 Volt Standby power to 'excite' the power supply, and turn it on.

The first chip to receive power is the BIOS chip.
[Chip and Chipset are slang terms for I.C.
Integrated Circuit.
BIOS stands for Basic Input/Output System]

BIOS,

http://en.wikipedia.org/wiki/BIOS ]

BIOS looks to see what devices are installed, does a Ram Memory count, TURNS the Processor on, and hands the computer over to the Operating System.
(Windows XP is one example of an O/S. Operating System)

The LED lights receive power, so do the fans, and the Harddrive. When it's time for the Processor to kick on, there isn't enough power, and the Power Supply 'falls to it's knees'.

Replace the Power Supply.
It's just one of the basic ATX power supply's that are readily available in a multitude of places.
The Wattage is 300 Watts.

The ATX form factor for this power supply, (Size and shape), is approximately 6 inches Long, 6 inches Wide, and 3-1/2 inches Tall.

Power cables needed:
(Continued in a Comment)

Try F2

CPU/Processor

• Socket: 939
• Supports the following processors:
  • AMD Athlon 64 X2 up to 4800+
  • AMD Athlon 64
  • AMD Sempron

CPU/Processor

• Socket: 939
• Supports the following processors:
  • AMD Athlon 64 X2 up to 4800+
  • AMD Athlon 64
  • AMD Sempron

CPU/Processor

• Socket: 939
• Supports the following processors:
  • AMD Athlon 64 X2 up to 4800+
  • AMD Athlon 64
  • AMD Sempron

Cpu/Processor Type
Socket: 939

• Supports the following processors:
  • AMD Athlon 64 X2 up to 4800+
  • AMD Athlon 64
  • AMD Sempron

You need and AMD motherboard that supports the Sempron processor -939 Socket. It's a little difficult to find them now, but they are still available. Since you have a brand computer. You make have to give up some perks like front usb port or the audio cable might be too short to mount on the new board. Be prepared for some compromise when installing a different board.

See Link:http://cgi.ebay.com/Compaq-SR1603WM-AMD-Sempron-1-8Ghz-1GB-160GB-DVD-RW-PC_W0QQitemZ270488804698QQcmdZViewItemQQptZDesktop_PCs?hash=item3efa639d5a

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Good luck

for better gaming performance u need a Graphics card of nvidia or abt 4 gb of ram....bt 1.8 ghz processor can't  go smoothly with High performance Games...so its better to change ur motherboard instead of wasting money on such things becoz only selected games will run on 1.8ghz processor...KSHITIJ

My best advice for this is to not buy it alone, or go in blindly. You should take it to a computer shop, even best buy - take it in with you and their team of experts will gladly help you.