Server OS

[code_glitch]

I'm finally getting round to building that all important server, based on a D510 motherboard (atom dual core with hyper-threading so 4 threads in total). It all comes down to around £170 for everything. However, it leaves one MAJOR gap: The server has to be able to use the WH1081 weather station sitting outside - and thats Millenium or later by M$ only. So the question is:

What would you use as a server os? Bearing in mind it also has to run PHP, Apache, Ftp, weather (cumulus) and dish out data at the end of the day; I had windows server in mind or possibly a REALLY sliimmed down version of vista (I got one running comfy on 128mb ram, celeron M (single core 1.8ghz) at one point) thanks to vlite... I'm not keen on xp for cache and security reasons as well as compatibility issues with software I run.

Any thoughts?

The specs are as follows:
1.66GhZ Cpu
2GB - 2.5GB depending on whether I find that spare 512 lying around and if it's compatible
500gb Western Digital Caviar Blue SATA 2 16MB cache@ 7200rpm
120watt (plenty) psu
all wrapped in a compucase 8K07BU for mini-itx

I do have doubts on the hard drive but the price goal is around £35.

Edit: The atom is the (funny enough) D510 chip with GMA 3150 (not really important) and I might blog the building with a few snaps perhaps... At least its cheaper that other Atom rigs like the eeeBox or Revo (around £280)... And if you dont need weather data, use ubuntu - its free. I just happen to have licenses for windows lying about randomly. Like when I upgraded my Vista premium x86 machine to 7 ultimate x64... I wonder why? No names mentioned *cough*Hp*cough* and bloatware =]