Freezes after a few hours of inactivity

After I wrote to the thread found this:

Maybe worth trying
Everyone, I hereby conclude that:

my desktop freezes if i checked "auto-hide the taskbar " on taskbar properties and wake my
computer after sleeping at least 1 minute OR
if i put the "turn off display after " setting to 1 minute and wait for like 2 - 4 minutes
so, these are things that might happen:
1. i disabled "auto-hide the taskbar" and disabled "turn off display after" OR i disabled
"auto-hide the taskbar" but didnt put my computer to sleep
with / without any open programs
result: desktop fine
2. i enabled "auto-hide the taskbar" and disabled "turn off display after" OR i enabled
"auto-hide the taskbar" but didnt put my computer to sleep
with / without any open programs
result: desktop fine
3. i disabled "auto-hide the taskbar" and enabled "turn off display after" OR i disabled
"auto-hide the taskbar" and put my computer sleep
with / without any open programs
result: desktop fine
4. i enabled "auto-hide the taskbar" and enabled "turn off display after" OR i enabled
"auto-hide the taskbar" and put my computer sleep
with a/some open program(s)
result: desktop fine
5. i enabled "auto-hide the taskbar" and enabled "turn off display after" OR i enabled
"auto-hide the taskbar" and and put my computer sleep
without any open programs
result: desktop freezes
my pc spec:
OS: : win 7 ultimate 7600.16385.rtm.x64 (clean install)
CPU: : Intel® Core™2 T5200 @1.60 GHz
RAM: : 1Gb
Video Card: : Ati Mobility Radeon X1400
Windows Experience Index : 3.4 (basescore)

Welcome to Microsoft Answers Forum!
Methods I would recommend are:

Method 1:
Update the graphics driver. Steps to update graphics driver:
i. Click Start, type devmgmt.msc and press enter.
ii. Expand Display adapter and right click on the sub item and click update driver.

Method 2:
You can change the power settings and check if that helps
i. Right click on the desktop
ii. Select Personalize
iii. Click Screen saver
iv. Under Power management category select Change Power setting
v. Select Balanced and select Never under these two option: a)Turn off the display
b) Put the computer to sleep

If that does not help then try changing the screen saver on your computer and check if
that helps, steps to follow
i. Select Control Panel from Start menu
ii. Select Appearance and personalization
iii. Select Personalization
iv. And the choose Screen saver
v. Select None from the dropdown list

Method 3:
Boot in clean boot to check which third party is causing the problem. To help troubleshoot
error messages and other issues, you can start Windows 7 by using a minimal set of drivers and
startup programs. This kind of startup is known as a "clean boot." A clean boot helps eliminate
software conflicts.
Steps to perform clean boot and check if you have the issue.

i. Click Start, type msconfig in the Start Search box, and then press ENTER.
ii. If you are prompted for an administrator password or for a confirmation,
type the password, or click Continue.
iii. On the General tab, click Selective Startup.
iv. Under Selective Startup, click to clear the Load Startup Items check box.
v. Click the Services tab, click to select the Hide All Microsoft Services
check box, and then click Disable All.
vi. Click OK.
vii. When you are prompted, click Restart.
viii. After the computer starts, check whether the problem is resolved.

If the issue is resolved check which third party is causing the problem, referring the link
given below: How to Troubleshoot a Problem by Performing a Clean Startup in Windows 7 or Vista

Reset the computer to start as usual
After you have finished troubleshooting, follow these steps to reset the computer to start as
usual:
i. Click Start, type msconfig.exe in the Start Search box, and then press
ENTER.
ii. If you are prompted for an administrator password or for confirmation, type
your password, or click Continue.
iii. On the General tab, click the Normal Startup option, and then click OK.