Perplexed!!  A few weeks ago, I noticed some odd performance events after being on the internet for AWHILE.  Now, it has gotten much worse.  I have a HP computer with XP Pro.  Here are the symptoms:
1.  It begins after actively using the internet for a 2 or 3 hours.
2.  Text and graphics on pages start to blank out in various places on the screen PAGE.  As you hit refresh, the blank areas move around and about.  The minimize sessions at the bottom can blank out.  Efforts to do anything give unpredictable displays.
3.  In the beginning it seemed that deleting internet temp storage using "tools" helped      eliminate the problem but now, when possible to use, it doesn't seem to always work.
Even that delete option window starts to be unresponsive and starts blanking out.
4.  All system restore points are gone as if wiped out.  After I reboot, I can set a new restore point and it and any others set stays on until the problem reoccurs again - then gone!
5.  There have been a couple of times when I go to the "stand by", "turn off", "restart" window, and click on one, the system does not respond and I have to simply power off.
6.  When I reboot, the problem is gone except for the desktop icons mentioned next.
7.   My desktop now has a series of odd icons added to it.  The number can vary from 3 to   10.  Each one has a square at the top with a smaller square in the center with what appears to be EXTREMELY tiny icons INSIDE (can't really see well).  Under that larger main square, there is a series of smaller squares in two rows that vary in number.  There may be 5 in one row and 8 in the second row.
8.  I ran an AVAST scan and found two items listed.  The first was simply a statement about insufficient storage.  I couldn't click on it.  The second was a setup file name identified with a virus named "Sality".  On it I was given several options so I selected the "repair" one and it came back complaining about insufficient storage.  So I then selected the quarantine "chest" option for the file.  It worked but did not fix the problem.
9.  I ran some Malware programs and found no issues.  Ran CCleaner to remove listed temporary storage types but was surprised to see a large number of used storage there.
10.  Looked at both of my disk drive properties and both have a HUGE amount of free space.  I have 1024 RAM. 

I appears if I just reboot every couple of hours of internet use the problem would not occur.
What is reboot doing to fix it?  Any ideas appreciated.Here's An Update:  The problem reappeared.  All symptoms the same with this additional information. 
1.  When the blanking out and reappearing of the text/graphics of the page I'm on occurs I noticed it does so as I circle and move the mouse cursor around on the page.
2.  I clicked on one of the odd icons the error added to my desktop and was presented with a "Open With Window" heading window.  Under the heading there was "Choose The Program You Want To Use To Open This File".  Under that was the word "File:" followed by a series of squares that appeared with the icon.  Under that was a list of 12 COMMON programs on my system (Adobe Reader, Family Lawyer, etc) you could check.
3.  I ran the Windows Chkdsk program in the repair mode on both my disks (drives C and D).  Some minor index deletes were listed by nothing significant.