(SOLVED) Taskbar thumbnail preview disappears quickly

Question

I have windows 7 RC on my laptop, Dell 1501.
When I start one or more programs from the taskbar and hover my mouse pointer on them I can see thumbnail previews.
The problem is that thumbnail previews disappear too quickly even though my mouse pointer is still on the opened program in taskbar.
I have to move my mouse so I can get another quick preview.
I notice that if I click on an empty space on the taskbar with the left mouse button, and then point to an opened program the thumbnail preview stays for as long as my mouse pointer is on the program.
Does anybody have that problem?
EDIT:
I notice something else,
if I open regedit or computer management and one of them is active, all other opened programs on the taskbar have long thumbnail preview.
But if for example windows explorer is the active window on taskbar, thumbnail previews stay for a short time.
SOLUTION: dell 1501 specific and may be bios version
1. shut down the laptop
2. remove the power supply and the battery
3. press and hold the power button (I pressed it 2-3 times and kept it pressed for about 1 second) --- obviously the laptop will not start.
4. plug in the battery and the power supply, start the laptop and check if the problem is gone.

Answer 1

teeqeela: "I can't believe it! Same dell, same problem, same solution. Thanks man!"
If that was for me, my pleasure.
Noel Carboni: "I'd be curious to know whether you've found the reason it was happening"
I'm curious about the reason, but not prepared to spend the time to find it; I don't think we'd learn enough from it to justify the time. Back pre-Windows pre-Internet I spent weeks painfully debugging. It's
hugely more complicated now, the Internet finds most things quickly anyway, and the tedious tracing doesn't bring many useful insights. I can't give answers, I'll just repeat the facts - any proposed answer must address them. Some details in the numbered points
I made a few messages back. The problem first manifested (for me, and I believe for others) some months after installing Win7 on Inspiron 1501 (specifically that machine). It's cleared by removing all power, and by a couple of software tricks (disable gadgets,
registry hack). Once cleared by power removal, it stays clear for weeks (not months) then recurs (don't yet know how permanent other fixes will turn out to be). One thinks of things such as some bit in system memory that gets set somehow, and never reset until
power is removed (it might be a memory location always alive and watching for a wake-on-lan or other wakeup event), which Win8 expects to find reset. But why the month's delay? Win7 (32- and 64-bit) works fine on Inspiron 1501, but is not officially supported,
and some non-Dell drivers must be used; they work fine. I could go on till the cows come home, but I've got myself a usable machine, and told others about it, so that's it.
HTH,
pol098