Running 4 installs on a quad-core with 4GB on Vista 64. Runs great. Doubt any more RAM will make a difference.

Tweaking Vista a bit can help though. I'll paste the "how to speed up Vista mail" I send to colleagues when they come bitchin' below. As always, use at your own risk and don't blame me if anything goes wrong.....but it should all be pretty safe.

-edit-
Step 4 is obviously not needed if you have 4GB already.

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1. Turn off Windows Search Indexing Windows Vista search indexing is constantly reviewing files on your system to make their contents available for quick searching. This is handy, but can severely impact system performance.

To disable this constant indexing:
- Click Start then Computer
- Right Click the C: Drive
- On General Tab, Uncheck Index this drive for faster searching
- On the subsequent dialog box, Select Include subfolders and files

2. Turn off Automatic Windows Defender Operation. Windows Defender real-time protection against malware continues to run despite having automatic operation disabled.

To disable this feature:
- Open Control Panel
- Select Windows Defender
- Choose Tools from the top menu
- Select Options
- Uncheck Auto Start at the bottom of the window

3. Turn off Automatic Disk Defragmentation Windows Vista and its always-on defragment feature isn't really that necessary and can cause system slow down. Just remember to run a defrag manually every week or so.

To disable this:
- Click Start then Computer
- Right Click the C: Drive
- Select the Tools Tab
- Uncheck Run on a schedule

4. Add a 2GB or higher USB Flash drive to take advantage of Windows Ready Boost (Additional Memory Cache). Ready Boost is Microsoft's name for using a USB thumb/flash drive to provide some quick access memory the operating system can use as extra RAM. The Ready Boost system can significantly improve system performance.

To set this up:
- Insert a USB Flash Drive (preferably 2GB or more)
- Click Start then Computer
- Right Click the USB Drive in My Computer
- Select the Ready Boost Tab
- Choose Use this device
- Select as much space as you can free up for RAM usage vs. Storage

5. Turn off Windows Hibernation
Windows hibernation background services can use a large amount of system resources. If you don't use the Hibernate feature on a regular basis you may want to disable it to give Vista a performance boost.

To disable Hibernation:
- Select the Contro- Pane- then Power Options
- Click Change Plan Settings
- Click on Change Advanced Power Settings
- Expand the Sleep selection
- Expand the Hibernate After selection
- Crank the selector down to zero
- Click Apply

6. Turn off System Restore
Analysis and restore point creation by Windows Vista can eat a fair amount of system resources. Disabling this service will obviously mean the system restore feature in Vista will not be available in the event of a system crash. Change this at your own risk.
- Control Panel > System
- Click System Protection on the left panel
- Uncheck the main system drive
- Agree to the confirmation

7. Disable User Access Control (UAC)
This much-loathed new Vista feature attempts to protect your system from malware infection by making you manually confirm a whole host of everyday user operations. While it doesn't directly impact performance, it can be annoying and might be more hassle than good.

To disable User Access Control:
- Click Start then Contro- Panel
- Select User Accounts
- Select Turn User Account Control on or off
- Uncheck User Account Control Box
- Restart as recommended

8. Disable excess Windows Services that Auto-Launch at Startup Just like Windows XP, Vista ships with all kinds of services enabled that load at startup and may never be used by most users. To see what loads at startup and disable the ones you likely won't be needing (they can always be started manually later):

- Click Start then Control Panel
- Select Administrative Tools
- Choose System Configuration
- Click the Services Tab
- You can safely deselect:
¡ Offline Files (unless you're using Offline File Sync) ¡ Tablet PC Input Service (unless you have a tablet PC) ¡ Terminal Services ¡ Windows Search (If you have already disabled indexing) ¡ Fax (unless you're using a fax modem)

9. Disable Excess Windows Features
Windows ships with other features that are listed separately in the Vista operating system from the startup services.

You can view and disable these features by:
- Clicking Start then Contro- Panel
- Select Program Features
- On the left panel, select Turn Windows Features on or off
- You can safely deselect:
¡ Indexing Service
¡ Remote Differential Compression
¡ Tablet PC Optional Components
¡ Windows DFS Replication Service
¡ Windows Fax & Scan (unless you use a modem for faxing) ¡ Windows Meeting Space (unless you use the Live Meeting Service)