My server very slow after upgrade XAMPP

[vbg]

I upgrade my server with XAMPP for Windows Version 1.5.4 (Apache 2.2.3, MySQL 5.0.24a, PHP 5.1.6) and Moodle 1.6.2. But, now the server is very slow (or stop) with a few on-line users... I think this is not related with Moodle…
Before, the server had Xampp 1.5.1 and Moodle 1.4.5 and works fine...
Other features of my Server:
Double Pentium II
Windows 2000 SP4
RAM = 262 Mb
2,5 Gb free space on Disk

Anyone can help me please? Thanks...