Compilation speed in Windows XP guest

[CadentOrange]

I've recently migrated my development VMs to VirtualBox and I've noticed that the compilation performance is about 3x slower than what I'm used to with competing products running on the same hardware. I'm not sure what it could be, as my guest CPU usage never exceeds 50% and I've got more than enough memory free on both the host and guest.

The VM details:
* Windows XP SP3, 32 bit
* 2 CPU, VT-x and Nested Paging enabled.
* 2048 MB RAM
* Guest Additions 4.3.10 installed
* Dynamically sized hard disk

The host details:
* OS X 10.9.2 Mavericks, 64 bit.
* Quad core i7-3615QM processor. Hyper threading enabled.
* 16GB RAM, SSD
* VirtualBox 4.3.10

Any help would be much appreciated.