Budget build work pc

i have been asked by a friend to help build a new works pc for her (self employed), primarily the pc is used for office 2007 apps, web surfing and some other apps that tend to slow the pc down alot,currently multiple applications mean a very slow pc.

the pc needs to run xp pro, have a 1tb drive and comfortably handle 2/3 apps at once.after some discussion she likes the nzxt beta evo case as the pc sits under her desk and has 2 usb on top.i recently built a new pc for myself following advice from people here which consisted of

350W Enermax ECO80+ psu
ASUS M4A785TD-M EVO MOBO
AMD ATHLON II X3 425 sAM3
4gb ddr3 memory

would a similar build be good for my friends needs as it falls into the budget that she has in mind (£300-£400) or would lookin at pc world etc be a better option (no monitor needed) or a better combination of components.
almost forgot to mention that the budget price needs to include the case,hdd,optical drive etc

That build looks fine to me IMHO.

Why not buy one off the shelf? Dell, HP etc.

It'll mean less support and if something goes wrong, less grief.

i am willing to look at shops to purchase from but considered builing one as i assumed i can get a better spec one if i built it for the budget given, if you have any suggestions please let me know