Key things you'll want...

Here are a few things you might want to install on your dedicated virtual machine for doing offers. This applies mostly to Points2Shop/Cashle but can be used on just about any other GPT or PTC site.

1. Fresh install of Windows XP - This is a must, when doing any VM or dedicated computer setup for doing offers, Windows XP is the most accepted for downloaded offers for toolbars, etc. I've found many apps so far that do not support Vista/Win7 and as far as speed goes, XP is a win in a virtual environment.
2. Fully updated XP (including latest IE) along with FireFox, Safari and Google Chrome - Most of the time I use FireFox for offers, but sometimes it seems to effect approval rating. When I seem to be in a points-slump (5 or more offers not approving in a 2hr period) I tend to move to Google Chrome or in some cases Safari. While the evidence is anecdotal at best, it does appear to work.
3. Disable/Remove firewall and DO NOT install Antivirus - This is a big must, first, its a virtual machine. Make sure you do NOT login to your banking website, your main email, etc. on it. Its for doing offers and general (non-personal) surfing. Your risk of getting infected is high but it will nto get to your main machine through the VM. Disabling firewall and not using AV has a positive effect on your approval rating, as scary as that is. 
4. Install CCLEANER - CCLEANER is a cookie and temporary files cleaner that works excellent for Windows XP/Vista/Win7. It'll not only clear your standard browser cookie and cache, but you can set whitelists to allow things like your P2S login, gmail login and what not so it doesn't clear them out. Additionally, it also clears out your Adobe FLASH tracking data, some offers use this to track you. 
5. Install other tools you might use - For example; I use twhirl for twitter, pwsafe for all my passwords and a few other tools. It all depends on your need.