If you are experiencing slow response times and poor video, I would suggest upgrading the RAM (Random-Access Memory) which is a type of computer data storage, increasing the RAM is one of the cheapest, fastest ways to boost your computer's performance. This is make multitasking much faster and smoother when multiple programs are running simultaneously and even when often switching between them, your computer will still run smoothly. Increased RAM supports colour at higher resolutions and gives you the power for enhanced 3D rendering, with amazing character realism font and texture versatility.
A dedicated graphics card has its own RAM and Processor specifically for processing video images, and offloads this work from the CPU and system RAM. I would suggest getting 2gb(x2) RAM, you can find this on http://www.amazon.co.uk/dp/B001R4BT1M/ref=asc_df_B001R4BT1M6303535?smid=A1JVOZ5RWQPGFB&tag=googlecouk0621&linkCode=asn&creative=22218&creativeASIN=B001R4BT1M
A Graphics Card can also improve the performance of your computer, and increase the resolution of your monitor, which will increase the video and response times. I would recommend a GeForce GTS 240 (Nvidia), it is relatively cheep, good performance and well-lasting. There are many different graphics cards available with different connection ports on the motherboard, with the GTS 240, the connection port is a PCI (Peripheral Component Interconnect). You can find this graphics card on http://www.amazon.com/nVidia-P361-Graphics-PCI-Express-Compatible/dp/B005JZQWEO
An other way of increasing your response time while gaming is getting a new monitor, this will increase your resolution to (depending on the graphics card), increase the refresh rate (the rate that the screen data is being refreshed, the higher the numbers the faster it refreshes.), response time and lower input lag. This together will improve your gaming experience. I would recommend an Alienware monitor, which you can find on http://accessories.us.dell.com/sna/products/Displays/productdetail.aspx?c=us&l=en&s=dhs&cs=19&sku=320-8846
Viruses is a price of software designed to deal harm to your computer, software or hardware. A virus can be hidden within any download-able software on the Internet, or even on web pages. You can stop a virus by having a firewall installed on your computer, or even the default system firewall switched on. If a virus gets past your firewall if could be hard to remove it, but if you have a anti-virus software installed, a good free anti-virus is Panda Cloud Anti-virus, which you can find on http://www.cloudantivirus.com/en/ It is free to download and easy to use.