Can anyone tell me what is the best spec for my needs.

I only use a computer for spreadsheet use.
I have 10 sheets open in one workbook.
Sheets are over 50,000 rows deep and 30 columns wide.
Array formulas run down several columns.

When I run macro to fill down array formulas the machine freezes.
Computer is AMD Athlon(tm) XP 2600+.

I have maximum of £400 but don't require monitor.

Any suggestions??
Thanks.
Colwyn.

For spreadsheet work, you really do not need a powerful machine.
I would recommend checking Dell or Hp's site for their cheapest Intel Core 2 based system with 2-4Gb of RAM.
For your intended usage, it will probably cost more to build it your self.
A quick look at Dell's UK site points me towards an Inspiron 530 for £299 shiped that would work great for you.
You really do not need anything to powerful and even a current Pentium Duel Core system with 2Gb of RAM would do what you need it to.

Thanks outlw, looks good - just a bit concerned about vista.
Colwyn.

No problem.

Not to try and push you either way with Vista but most of the issues plaguing it at release were fixed with the release of SP1. I made the jump about 3 months ago and was pleasantly surprised with how far it has come since it was first released.

In the worst case, you can format and reinstall your current copy of Xp on any prebuilt machine in a lazy afternoon.