Just leave your laptop as it is. They svck.
The first two things you should consider for a new rig are the PSU and the computer case. These two things are the most future proof components of any rig, so it ok to buy them early.
PSU:
Don't cheap out on your PSU. I recommend getting at least a 750 watt PSU, so you'll have enough watts to feed whatever power hungry devices come out in the future. Here are two lists of quality PSUs.
http://www.eggxpert.com/forums/thread/323050.aspx
http://www.overclock.net/power-supplies/183810-faq-recomended-power-supplies.html
Running Total: ~$100 USD
Case: Don't get anything less than a full tower. The only limit to your rig should be the money in your pocket, not the size of your case. The standard full-tower is the HAF 932.
Running Total: ~$230 USD
Monitor:
For gaming, you'll want a true 120Hz monitor. TRUE 120Hz monitors will display 120 frames per second vs the standard 60 FPS from 60Hz. Your picture will be smoother which gives you a significant advantage. Here's a link that lists true 120Hz monitors: http://www.nvidia.com/object/3d-vision-requirements.html
Running Total: ~$550 USD
Mouse:
The Logitech MX518 and the Razer Deathadder are the best two mice EVER made. Don't get anything else.
Running Total: ~$600 USD
Keyboard:
The thing to look out for in keyboards is "how many keys you can press at the same time before the keyboard just starts ignoring you." Open up notepad and try it with your current keyboard. Press and hold down a letter, then another letter, then another. For gaming, you want to be able to press a lot of keys at the same time. This is known is Key Rollover or NKRO (the higher the better). Next I've got to tell you about mechanical keyboards. The keyboards most of us are using are rubber domes. That means under your keyboard is something that looks like this:
There are lots of reasons why people say they svck. You can look them up yourself. The alternative is to get mechanical keyboard (this is how they made keyboards back in 1985. You'll want to get yourself a mechanical keyboard with brown switches. They offer the best balance between typing and gaming. If you MUST get a rubber dome keyboard, the sidewinder x4 is the best option as it offers the highest key rollover. Use the PS/2 connection instead of the USB if your keyboard offers it. For mechanicals, this company called XArmor is releasing the U9BL-s, which will probably be the least expensive brown switched keyboard on the market.
Running Total: ~$680 USD
Sound:
Headphones will give you a lot more sound quality for the price vs. speakers. So go with headphones. If you want to spend 50$, don't get anything other than the JVC HA-RX700s. Further up the price ladder, your choices expand to the ATH-AD700s and the Sennheiser HD555. You'll need a sound card as well. I slightly recommend getting a PCIe sound card, because of the way todays mother boards are designed. If you get a PCI card rather than a PCIe card, you'll end up blocking one of your other PCIe slots, which can come back to haunt you. The best inexpensive sound card is the ASUS Xonar DG (PCI). As you climb up the price ladder your choices expand to the Xonar DX and crazy over priced ones you probably don't want to spend money on.
Running Total: ~$800 USD
Graphics:
There is no video card that can max out crysis at 60 FPS yet. Anyway, 99% of games are being developed for the xbox360's crappy hardware, so there's no need to overspend on your GPU. Besides, if you ever game competitively, you're going to use low graphics and low resolutions anyway (especially in crysis). That said, because you're getting a 120Hz monitor, you do want a GPU solution that'll give you at least 120 FPS on all low settings and minimal resolution. A GTX 460 will handle that for you in about 90% of games (just not crysis).
Running Total: ~$950 USD
Memory/RAM:
Just make sure the RAM you get is at least 1600MHz, anything less will limit your potential overclocks. Get at least 4GB. Some CPUs prefer "tri-channel" memory (that just means they want you to use three memory sticks instead of two). For those, get 6GB.
Running Total: ~$1050 USD
CPU:
The CPU will determine what kind of motherboard you have to buy and what your RAM configuration should be. I'd say get nothing less than the i5-750 / i7-920. Crysis in particular is a VERY CPU hungry game. You want the best CPU possible, and you WILL have to overclock it to at least 4.00GHz.
Running Total: ~$1275 USD
Motherboard:
You'll need one.
Final Total: ~$1500 USD
Sorry about your wallet! There are ALWAYS sales for computer parts. So with rebates etc. you won't be paying anywhere near this much.
£805.00 sample rig (without GPU) using Aria.co.uk and Amazon.co.uk.
PSU: OCZ StealthXStream 2 700W - £67.38
http://www.aria.co.uk/Products/Components/Power+Supplies/700-950W/OCZ+StealthXStream+2+700W+Power+Supply+?productId=40945
Case: HAF 932 - £104.99 This is ridiculous. Shop around and you'll find a better price guaranteed.
http://www.aria.co.uk/Products/Components/Cases/Full+Tower/CoolerMaster+HAF+RC-932+Gaming+Full+Tower+Case+-+Black?productId=33726
Monitor: Samsung SyncMaster 2233RZ - £189.00 (If I could only convince you to buy one thing, it would be this. beautiful monitor)
http://www.amazon.co.uk/Samsung-SM2233RZ-Monitor-Gloss-Black/dp/B001TH77I6/ref=sr_1_1?ie=UTF8&s=computers&qid=1297043133&sr=8-1
Mouse: Logitech MX518 - £26.00
http://www.amazon.co.uk/Logitech-MX518-Optical-Gaming-Mouse/dp/B0015R8M7U/ref=sr_1_1?ie=UTF8&qid=1297041611&sr=8-1
Keyboard: Sidewinder x4 - £33.59
http://www.aria.co.uk/Products/Peripherals/Keyboards/Gaming+Keyboards/Microsoft+Sidewinder+X4+USB+Gaming+Keyboard+-+Black+%28JQD-00006%29?productId=40170
Sound card: Xonar DG - £26.00
http://www.amazon.co.uk/ASUS-Xonar-PCI-Audio-Card/dp/B003ZXDOL6/ref=sr_1_1?ie=UTF8&s=miscellaneous&qid=1297041722&sr=8-1
Memory: 4GB Corsair XMS3 - £38.99
http://www.aria.co.uk/Products/Components/Memory/DDR3+Dual+Channel+-+PC3-12800/4GB+Corsair+XMS3+%282x2GB%29+DDR3+PC3-12800C9+1600MHz+Dual+Channel+Kit+-+CMX4GX3M2A1600C9+?productId=37570
CPU: i5-2500k - £169.19
http://www.aria.co.uk/Products/Components/CPUs+%2F+Processors/Intel+Core+I5+%281155%29/Intel+Core+i5-2500K+3.30GHz+%28Sandybridge%29+Socket+LGA1155+Processor+-+OEM+?productId=43635
Motherboard: ASUS P8P67 Pro or Gigabyte GA-P67A-UD4 - £147.00
http://www.aria.co.uk/Products/Components/Motherboards/Intel+1155+P67/ASUS+P8P67+Pro+Intel+P67+%28Socket+1155%29+DDR3+PCI-Express+Motherboard+?productId=42939
http://www.aria.co.uk/Products/Components/Motherboards/Intel+1155+P67/Gigabyte+GA-P67A-UD4+Intel+P67+%28Socket+1155%29+DDR3+PCI-Express+Motherboard+?productId=42994
Well that was quite a mouthful.