Plzz help me guys I am going to buy a 1gb graphics card and I have 1gb system memory, will it cause any problems??

Impossible to tell with such scant information.

NO

Why?

Because a graphics card has it's own Processor, and RAM.

The Processor is a G.P.U.

Graphics processing unit - Wikipedia, the free encyclopedia

Also known as a graphics chipset.

It doesn't need to borrow from the system resources. The Processor and RAM on the motherboard.

This is why, for one example, you can have a computer with 1GB of DDR2 Sdram RAM, and a graphics card that uses GDDR3, or GDDR4, or GDDR5 graphics memory.

The things you need to be concerned with are;

1) Do you have the correct expansion slot on the motherboard, for the graphics card?
PCI or AGP, or PCI-Express x16?

2) Does you Power Supply have enough power for BOTH the graphics card, and the rest of the computer system?

Post back with the manufacturer name, and Model Number, of the Desktop PC.
Also post the manufacturer name, and Model Number of the graphics card.

Regards,
joecoolvette

To Add:
Chip and Chipset are slang terms for I.C.
Integrated Circuit,

Integrated circuit - Wikipedia, the free encyclopedia

WHEN installing a graphics card, ALWAYS install the graphics card's software F-I-R-S-T!
(Graphics card's Installation CD Disk)

THEN unplug power to the computer, FOLLOW Anti-Static Precautions, and physically install the graphics card.

Why?
Because when a device is installed on a computer, (In this case the device is a graphics card), Windows will 'break it's neck', to find suitable drivers.

If THE drivers are not there, Windows will match up one of it's THOUSANDS of generic drivers.

This = No

The graphics card needs IT'S drivers made for it.

Install the software after installing the graphics card?

Driver Conflict.

Windows: "Which drivers do I use? These or THESE?"

(These = Windows generic drivers
THESE = THE drivers for the graphics card)

Post additional questions.

Regards,
joecoolvette

Drivers are small pieces of software, that allow an Operating System to 'Communicate' with a device.

Windows XP and Windows 7 are two examples of an O/S.
(Operating System)
The graphics card is an example of a device.

Device driver - Wikipedia, the free encyclopedia