OP: What kind of computer do you currently have?
Here are some computers that I've tested the game with:
My old Pentium Dual-Core E5300 (LGA775) with a GT 240 OC 1GB gave me 60 fps on a packed TC server (30 drivers with a 800 object layout) maxed out, but it couldn't handle recording with FRAPS. This was at a resolution of 1366x768. 4Gb DDR2 667 RAM. Patch 0.6B
The same Pentium as above but with the NVIDIA 7050 integrated graphics, 45 fps max online, patch Z28.
A Pentium 4 2.4GHz(478) machine with a NVIDIA Geforce4 MX420 64mb managed 14fps on lowest settings at 1024x768 on a TC server with about 12 people online, with 800 objects. 256mb DDR 300 RAM. Windows XP SP3. Offline FPS: 30. Patch 0.6B
A Pentium 4 2.8GHz HT (478) machine with an ATi Radeon X1650 Pro 512mb AGP managed 45fps at 1024x768 on a TC server with 15 people and 500 objects. 512mb DDR 333 RAM. Windows XP SP2. Offline FPS: 60. Patch Z28. (PC's hard drive corrupted before 6B came out)
A Core i5-2430m 2.4GHz (TB 3.0, HM67) HT (it's a slow i3-2125) with the Intel HD Graphics 3000 cannot run the game vanilla due to a graphics bug. I can run it with NightMod, however. Cannot start the game with anti-aliasing enabled (starts with endless black screen). Plays on a packed TC server with NightMod, maxed out but no AA at 25-30fps at 1366x768. 6GB DDR3 1333 RAM. Offline: 60-90. Patch 0.6B, nightmod for 0.5Y.
When I open the view tab in the vanilla installation, the game crashes. I get 15fps max for some reason....it's really odd.
Note that the HD Graphics 3000 only supports up to AA x4, versus NVIDIA and AMD supporting x16.
If you want to build a new PC for LFS, then get a Celeron G530, 4GB DDR3 ram, any hard drive/SSD, and any $100 graphics card, though AMD cards like the 6770 support Eyefinity for up to 6 monitors on one card.
The Celeron boasts great single core performance which is really what LFS needs, plus an average graphics card to make the game look extra pretty.
Really a 10 year old pc can run this game...maybe not very well, but it's possible.
**Note: Offline means BL1 with no AI, just racing around lonely.